FBI urges renewal of surveillance measures after foiled al-Qaida plot FBI director Robert Mueller told the House judiciary committee the new bomb was similar to previous devices. Photograph: Mark Wilson/Getty Images The head of the FBI has said his agency was "exploiting" the seizure of an intact and advanced form of underwear bomb that Islamic militants in Yemen had apparently wanted to use in an attempt to target a US-based jet. Robert Mueller told a congressional hearing in Washington on Wednesday that the supposed plot, revealed by the Associated Press on Monday, demonstrated the need to renew surveillance provisions that expire at the end of the year. Details of the plot have been unfolding in the past few days. A sting operation in Yemen involving an undercover agent working for Saudi Arabian intelligence and the CIA ended with the sophisticated bomb being handed over to western intelligence. It is now being examined by FBI experts at its forensic labs in Quantico, Virginia. It is believed the device was likely made by al-Qaida master bomb-maker Ibrahim Hassan al Asiri, who is the assumed bomb-making chief for al-Qaida's offshoot, al-Qaida in the Arabian Peninsula (AQAP). Al Asiri is believed to have been the creator of an underwear bomb used in an attempt to blow up an airliner over Detroit on Christmas Day 2009, as well as explosives that were packed into printer cartridges bound for Chicago in 2010. In a hearing of the House judiciary committee, Mueller said the new bomb was similar to previous AQAP devices. "We are currently exploiting an IED (improvised explosive device) seized overseas which is similar to devices used by AQAP in the past," he said. The bomb is believed to have had no metallic parts and used explosive chemicals designed to evade modern airport security. However, US security officials have insisted that it could still have been detected by scanners and security agents following correct procedures in airports. Al Asiri is a Saudi Arabian, thought to be in his early 30s, whose talent for making hard-to-detect bombs is emerging as a major focus of western counter-terrorism measures. He is a former chemistry student who is thought to have survived a US drone attack last year. Richard Barrett, who heads the al-Qaida-Taliban sanctions monitoring committee at the United Nations, told Reuters news agency that he was "pretty certain" Al Asiri was the top suspect in the latest plot. "He has a particular skill for making things which are effective without being detectable," he said. The capture of the latest underwear bomb has prompted security concerns across the US that al-Qaida and its allies are still actively trying to launch a high profile attack on US soil. Mueller said that such militants remained the "top" terrorist threat to the nation. "Al-Qaida is decentralised but the group is committed to high profile attacks against the west," Mueller said. Fresh details have also emerged of the nature of the intricate operation that brought the valuable bomb into US hands. News reports have described an informant effectively working as a double agent who managed to convince AQAP in Yemen that they were willing to act as a suicide bomber on the mission. After having been given the bomb the informant, who was working closely with Saudi intelligence, managed to leave the country safely and turn the device over to handlers. The informant's identity, and even their gender, has not been released. It has also been revealed that the capture of the bomb was not the only intelligence coup to emerge from the operation. A suspected American drone strike in Yemen at the weekend apparently killed two Islamic militants, including top militant Fahd Mohammed Ahmed Quso. The pair were targeted while driving a car in a missile strike that is believed to have acted upon information gathered by the informant. Quso had been on the FBI's most wanted list for his role the 2000 bombing of the USS Cole, which cost the lives of 17 sailors. There was a US bounty of $5m for his capture. The sting operation in Yemen is believed to have lasted for some time. President Barack Obama was informed of the plot in April, and its culmination - with the handover of the bomb - is thought to have happened perhaps as long as ten days ago. US security officials have insisted that the sting worked so well that they were confident that at no time was there any direct chance of the attack being carried out and there was no threat to any US aircraft. However, some US politicians, who have been briefed by security officials, have warned that the success of the operation does not mean the end of the threat from such devices. The obvious question right now is, how many more of these bombs are out there? They don't usually build just one; they build multiple," Congressman Michael McCaul told the Los Angeles Times. Yemen and its bomb-makers have now emerged as a major focus of Islamic militant activity. The country is riven by domestic unrest and parts of it have fallen under the sway of al-Qaida militias. Al-Qaida's own English-language web magazine Inspire has boasted of an AQAP bomb factory in Yemen that is using chemicals captured in recent territorial gains in the country. "The modest lab has transformed into a modern one," the article said. In his testimony to Congress, Mueller said that the latest incident was a reminder of the need to disable the threat from Yemen. "It demonstrates the need to address those responsible for the the production of those devices in Yemen," Mueller said.