A fire burns at the site of a CSX freight train derailment, Tuesday, May 28, 2013, in White Marsh, Md., where fire officials say the train crashed into a trash truck, causing an explosion that rattled homes at least a half-mile away and collapsed nearby buildings, setting them on fire. This still taken from video provided by James LeBrun shows an explosion outside Baltimore on Tuesday, May, 28, 2013. Baltimore County fire officials say a train derailed in a Baltimore suburb on Tuesday and an explosion was heard in the area. A fire spokeswoman says the train derailed about 2 p.m. Tuesday in White Marsh, Md. AP Photo/James LeBrun This image provided by WBAL-TV, shows a train derailment outside Baltimore on Tuesday, May, 28, 2013. Mark Paugh carries his 15-month-old son Ryan as they watch smoke from a train derailment in White Marsh, Md., Tuesday, May 28, 2013, in Rosedale, Md. A CSX cargo train crashed into a trash truck and derailed Tuesday in a Baltimore suburb and the explosion that followed rattled homes at least a half-mile away and collapsed nearby buildings, setting them on fire, officials and witnesses said. This photo provided by Dale Walston, shows an explosion outside Baltimore on Tuesday, May, 28, 2013. AP Photo/Kevin Lindemann (AP) - A CSX freight train crashed into a trash truck and derailed Tuesday in a Baltimore suburb and the explosion that followed rattled homes at least a half-mile away, sending a plume of smoke into the air that could be seen for miles, officials and witnesses said. In the third serious derailment this month, the dozen or so cars went off the tracks at about 2 p.m. in Rosedale, a Baltimore eastern suburb. Hazmat teams were on the scene, but Baltimore County Executive Kevin Kamenetz said at a news conference that no toxic inhalants were burning. Officials did not order an evacuation. The truck driver was taken to the hospital in serious condition and two CSX workers aboard weren't hurt, fire officials said. Dale Walston said he lives about a half-mile away and that he thought he could smell chemicals. "It shook my house pretty violently and knocked things off the shelves," he said in an email to The Associated Press. Even an hour after the blast, the thick plume of black smoke drifted across the Baltimore city line and covered the eastern part of the city. The face of one warehouse near the train tracks blew off. Shortly after 6:30 p.m., the plume lightened considerably, changing from black to gray, and its intensity diminished. Firefighters had been battling the flames for an hour and a half after initially considering letting the cars burn out. CSX spokesman Gary Sease said in an email that sodium chlorate is on one of the trains, which the Department of Transportation classifies as a hazardous material. However, Baltimore County Fire Chief John Hohman said the chemical is not in one of the cars that was burning into the evening. The bleaching agent is used in making paper. Nick Materer, an Oklahoma State University chemist and chief science officer at ExploSafe LLC in Stillwater, Okla., said sodium chlorate, when combined with fuel, makes a more volatile mixture. "When you mix them together and add fire they go boom," he said in a phone interview. Materer said the chemical is usually shipped as a white powder but it can also be in a liquid solution. Either way, he said, the fumes can irritate the lungs if inhaled. Earlier, fire officials had said buildings had collapsed, but Hohman modified that to say two warehouses were heavily damaged by the explosion and other buildings were harmed, but none collapsed. An Amtrak spokeswoman said its Northeast Corridor service was not affected. Kevin Lindemann, 29, a salesman for industrial pipe supplier Baltimore Windustrial near the tracks, said he and about 10 co-workers felt the ground shake, ran to a window and saw several cars on their sides and flames he estimated were 50 feet high. "You could feel the heat as soon as you walked out the door," Lindemann said. "We kind of panicked pretty quick," he said. We didn't wait around to see what was happening. So as soon as we saw the flames I took a quick picture and got in my truck and drove away. I wasn't sticking around for the explosion. Everyone left the building and drove several blocks away. Then they heard the explosion, five to 10 minutes after the derailment, he said. Even like three blocks away, it was loud. I mean, it just about took you to your knees," Lindemann said. Exactly what triggered the explosion was being investigated, and Hohman said firefighters were informing residents of about 70 nearby homes that they could leave if they choose and shelter will be provided. However, no one was being forced to evacuate. Derailments have done great damage before in Baltimore, a city with countless train tracks. Twelve years ago was the derailment and chemical fire in Baltimore's Howard Street tunnel. Rail cars burned for five days underground in July 2001. Portions of downtown were closed and rail traffic across the U.S. was affected for days. CSX eventually agreed to pay Baltimore $2 million to help defray the city's cleanup costs. The National Transportation Safety Board and the Federal Railroad Administration were sending teams to investigate Tuesday's crash. Photos showed at least a dozen train cars off the tracks, including at least one tanker car. Sease said four of the cars believed derailed carried terephthalic acid, which is used in the production of plastics and polyester, among other things. He said it is not listed as a hazardous material. One of the cars still burning was carrying terephthalic acid, and another was carrying fluoroacetic acid, Hohman said. Fluoroacetic acid can be used as a pesticide. Hazardous materials moving through Baltimore and elsewhere in Maryland was the subject of an agreement a few years ago between the state and CSX. After a November 2007 derailment involving a freight train carrying hazardous materials near Camden Yards, CSX agreed to give security officials real-time information about potential harmful cargo moving through the state on freight trains. Railroads had previously guarded such details as proprietary information. Also hit by a serious derailment this month was Bridgeport, Conn. On May 17, more than 70 people were injured when a commuter train went off the tracks. The eastbound train from New York City derailed during evening rush hour, came to a stop and was struck about 20 seconds later by a westbound train. In Rockview, Mo., on Saturday, a cargo train crash injured seven people and destroyed a highway overpass that could take a year to repair. Despite the high-profile railroad accidents, the overall number of such crashes has been declining industry wide and for CSX over the past decade. Last year was the safest year on record for the railroad industry, according to the railroad administration. All train accidents are down 43 percent since 2003, and derailments are down 40 percent over the same period, according to data provided by the administration. Freight train derailments specifically are also down 40 percent. In each of the past five years, CSX has reported more than 100 deaths in accidents and incidents involving the railroad. CSX, based in Jacksonville, Fla., operates over 21,000 miles of track in 23 eastern states and two Canadian provinces. Its shares traded higher Tuesday before the derailment was reported. The shares closed down 20 cents at $25.30. Bertha Pressley and her husband Tom Brown said their townhome in Middle River, about 3 miles away, shook and they initially feared a bomb or natural disaster. "I thought it was terrorism," Pressley said. Associated Press writers Kasey Jones in Baltimore, David Dishneau in Hagerstown, Josh Funk in Omaha, Neb., and Joan Lowy in Washington, D.C., contributed to this report.