Investigators probing into the failed bid by an alleged Al Qaeda operative to blow up a US plane are trying to figure out what type of explosive or chemicals he sneaked inside the aircraft that could not catch the attention of the security check points.

They are questioning the suspect -- 23-year-old Nigerian national identified as Umar Farouk Abdul Mutallab -- to find out how the explosive was made and how much threat it poses to the air security of the country.

The explosive material used by the Nigerian national apparently did not produce enough of an explosion to fire or bring down the plane.

According to CBS news, the suspect apparently used a syringe to inject a chemical into powder located near his groin. Such a technique has not been seen in previous attempted attacks, the report said.

It's possible that this incident was a test of whether the materials could pass screening and how effective they might be at causing damage, the official said.

"It raises some serious questions, such as how this person was able to bring an explosive substance aboard a commercial airliner?" Senator Susan Collins of Maine, the senior Republican on the Senate Homeland Security Committee, said.

A White House official termed it as an attempted act of terrorism.

The Nigerian national told the investigators he was given the device by Al Qaeda operatives in Yemen, along with detonation instructions, he said.

"This guy claims he is tied to the Al Qaeda, specifically in Yemen. He claims he was on orders from the Al Qaeda in Yemen. Who knows if that's true?" the official was quoted as saying by The Wall Street Journal.