WASHINGTON (Reuters) - The U.S. military is testing to see if a chemical agent may have been used in a rocket attack in Iraq by Islamic State that came within hundreds of yards (meters) of U.S. forces but injured no one, a U.S. military official said on Wednesday.

The rocket fell on Tuesday in an unpopulated area near the Qayyara West base, where hundreds of U.S. forces are working to prepare an airfield ahead of Iraq’s offensive to retake the city of Mosul from the radical group Islamic State, said the official, who spoke with Pentagon reporters on condition of anonymity.

A group of U.S. forces inspected the fragments afterwards and took a small sample of a suspicious “tar-like, black, oily” substance, which initially tested positive for mustard agent but then tested negative in a subsequent examination, the official said. Further tests were underway. The incident was first reported by CNN.

As a precaution, they underwent routine decontamination procedures, including showers, but did not display symptoms that would typically show up within 12 hours of exposure.

“It’s been more than 24 hours and we haven’t seen anyone who has any indication of blistering or anything like that,” the official said.

“There are absolutely no injuries. Nobody has been off their typical work schedule. It hasn’t impacted the mission in any way.”

The U.S. military has used air strikes to repeatedly hit Islamic State’s chemical weapons stores, and experts have warned that the militant group might use the agents during the upcoming Mosul offensive.

The United States has also observed repeated Islamic State attacks over the past year or so against Iraqi troops, Kurdish forces and Syrian soldiers, a second U.S. official said. But the official stressed there had not been such attacks against the U.S. forces in Iraq, who number at least 4,400.

“I don’t know of a case like this where it was proximate to U.S. forces like this before,” the second official said.

The first U.S. official described the group’s technical skills as crude when it came to mounting a chemical weapon attack and appeared to play down any growing concerns about a threat to U.S. forces.

“We have a moderate level of concern ... on a day to day basis and our concern isn’t much greater after seeing this, because it falls into the expected realm,” the official said.

The security protocols at the base have not changed as a result of the attack, the official said.</s>Islamic State may have used chemical weapon on U.S., Iraqi troops -CNN

WASHINGTON, Sept 21 (Reuters) - Islamic State forces fired a shell that may have contained a chemical agent onto a military base in northern Iraq on Tuesday while U.S. and Iraqi troops were present, CNN reported on Wednesday, citing several U.S. officials.

No U.S. troops were hurt in shelling at the base, which is being used to prepare an attack to retake Mosul from Islamic State, CNN said. The first test came back positive for a mustard agent but the second test was negative, it said. (Reporting by Eric Beech; Editing by David Alexander)</s>Islamic State rocket attack on US forces might have contained mustard agent

WASHINGTON – The Islamic State group has attacked U.S. and Iraqi troops using a rocket that initially tested positive for mustard agent, the Pentagon said Wednesday.

The attack took place midday Tuesday at Qayyarah West Air Base in northern Iraq where U.S. and Iraqi forces are building up an operations hub to retake Mosul, Islamic State group’s stronghold in that country. The attack on Mosul is planned for October, officials have said.

No U.S. troops were hurt in Tuesday’s rocket attack.

However, a U.S. explosive ordinance team went through decontamination after a shell fragment from the rocket initially tested positive for mustard agent, the Pentagon said Wednesday.

After the rocket exploded in the base, the explosive ordinance team responded to assess the munition. The team noticed a residue on the shell remnants and an initial test showed the substance to be mustard agent, said a senior defense official who spoke on the condition of anonymity.

A second test on the substance turned up negative, the official said.

However, the Islamic State group has used a crude form of mustard agent against Iraqi or Kurdish forces in other attacks. The poor quality of the chemical agent could give a negative test result.

The fragment will undergo further testing to determine whether mustard agent was used, the official said.

None of the U.S. forces that came into contact with the shell have shown any signs of injury or contamination, such as blistering, the defense official said.

Hundreds of U.S. forces are deployed to Qayyarah West Air Base, the official said.

The base is regularly targeted with indirect fire, the official said. However, he said this was the first time mustard agent has been used against U.S. forces.</s>Chemical agent possibly found on rocket fired at US troops in Iraq

A rocket fired by Islamic State jihadists at US forces in Iraq may have carried a chemical agent, a US defense official said Wednesday.

No one was injured in Tuesday's blast near an airfield by the northern town of Qayyarah and no one showed any immediate signs of exposure to the suspected mustard agent, the official said.

Several hundred US troops are working with Iraqi partners to strengthen the airfield ahead of a push on the IS stronghold of Mosul.

The defense official, speaking on condition of anonymity, said an incoming round had exploded within the base perimeter during an "indirect fire" attack.

A small team of US troops later inspected the fragmented ordinance and found one bit with a suspicious, tar-like black oily substance that they tested in the field.

That initial test was positive for a "mustard agent." A second test was negative, and a third sample has been sent to a proper laboratory for definitive analysis.

The official downplayed the seriousness of the incident, saying the shell would have been "militarily ineffective."

"Our concern is not much greater after seeing this," he said.

Still, the troops who handled the fragments went through a standard decontamination procedure.

US-led coalition warplanes last week destroyed a factory near Mosul suspected of being used by IS to make chemical weapons.

Observers have repeatedly alleged IS has used chemical weapons, and the Pentagon has confirmed the jihadists have deployed chlorine and sulfur mustard devices.

Iraqi security forces, backed by coalition air power, are in the final weeks of "shaping" operations ahead of an assault to recapture Mosul, which IS seized in 2014 and which remains the jihadists' last main stronghold in Iraq.</s>Islamic State forces fired a shell that may have contained a chemical agent onto a military base in northern Iraq on Tuesday while U.S. and Iraqi troops were present, CNN reported on Wednesday, citing several U.S. officials.

No U.S. troops were hurt in shelling at the base, which is being used to prepare an attack to retake Mosul from Islamic State, CNN said. The first test came back positive for a mustard agent but the second test was negative, it said.</s>U.S. tests for mustard agent after rocket attack near Iraq base

WASHINGTON, Sept 21 (Reuters) - The U.S. military is carrying out tests to see if a chemical agent may have been used in a rocket attack in Iraq by Islamic State that came within hundreds of yards (meters) of U.S. forces but injured no one, a U.S. official said on Wednesday.

The military official, who spoke on condition of anonymity, said the first of two initial tests showed the presence of a mustard agent but the second did not. None of the U.S. forces who inspected the shell fragments have displayed symptoms of exposure to a mustard agent, the official added. (Reporting by Phil Stewart; Editing by James Dalgleish)</s>Islamic State may have used chemical weapon on U.S., Iraqi troops -CNN

WASHINGTON, Sept 21 (Reuters) - Islamic State forces on Tuesday fired a shell that may have contained a mustard agent onto a military base in northern Iraq used by U.S. and Iraqi troops, CNN reported on Wednesday, citing several U.S. officials.

No U.S. troops were hurt or have displayed symptoms of exposure to a mustard agent, CNN said.

One official said the agent had "low purity" and was "poorly weaponized," CNN reported. A second official called it "ineffective," the network said.

A U.S. defense official said troops had gone out to look at the shell after it landed on the base, which is being used to prepare an attack to retake Mosul from Islamic State, CNN reported.

Two field tests were conducted after the troops saw what they thought was a suspect substance. The first test came back positive but the second test was negative, the network said.

The Pentagon did not immediately respond to a request for comment. (Writing by Eric Beech; Editing by David Alexander and James Dalgleish)</s>IS rocket fired in Iraq may have contained mustard agent

WASHINGTON (AP) — A small rocket that landed on a military base in northern Iraq where hundreds of U.S. troops are working with Iraqi troops may have contained a mustard agent, a U.S. military official said Wednesday.

No one was hurt and U.S. officials are still testing a residue found on a metal fragment from the rocket.

The U.S. official, who discussed details of the incident on condition that he not be identified by name, told reporters at the Pentagon that the attack happened Tuesday at Qayara West air base. The base is a staging area for Iraqi forces preparing for an assault on Mosul, the city that has been the Islamic State's main stronghold in Iraq since 2014.

U.S. officials have been reluctant to say how many U.S. troops are advising and assisting Iraqi troops at Qayara West. The U.S. official who described Tuesday's rocket attack said "hundreds" of U.S. troops are there, but he would not be more precise.

The official said the attack was militarily insignificant. He said a small group of U.S. soldiers who inspected remnants of the rocket after it exploded found a black, oily substance on a fragment of metal. An initial test of the suspicious substance showed it contained residue of mustard agent, but a second test was negative.

The fragment has been sent to a laboratory for further testing, the official said.

Mustard agent in sufficient quantities and concentration can maim or kill by damaging skin, eyes and airways.

Earlier this month, a U.S. general said American warplanes had eliminated a "significant chemical threat" to Iraqi civilians by bombing a complex of buildings near Mosul that Islamic State militants had converted from pharmaceutical manufacturing to chemical weapons production.

Air Force Lt. Gen. Jeffrey Harrigian told reporters on Sept. 13 that the target was an Islamic State headquarters also used to produce lethal chemicals, possibly including chlorine and mustard gas. He provided no details on the chemical production.</s>The U.S. military says a rocket that landed within several hundred yards of U.S. troops at a base in northern Iraq may have contained mustard agent.

No one was hurt in the attack on Qayara West air base, according to a U.S. military official who discussed details on condition that he not be identified. Several hundred U.S. troops are on the base.

The official says the attack Tuesday was militarily insignificant. He says a small group of U.S. soldiers who inspected remnants of the rocket found a black, oily substance on a fragment of metal. An initial test of the substance showed it contained residue of mustard agent, but a second test was negative.

The fragment has been sent to a laboratory for further testing.

Israeli military says Palestinian teenager killed after trying to stab soldier

Iraqi forces being trained to recapture Mosul will be ready next month, Joint Chiefs chairman says

Kerry lashes out at Russia, calls for grounding of all aircraft over humanitarian routes in Syria
The U.S. military investigates yesterday's Islamic State rocket strike near the Qayyarah Airfield West to ascertain if a chemical agent was used.