A vehicle found by Kurdish fighters last week in the northern Iraq city of Irbil (search) may be a mobile weapons laboratory, U.S. officials said.

Senior defense officials told Fox News they are "confident" the vehicle was used to manufacture biological or chemical weapons agents.

The officials said the mobile biological weapons lab has been moved to the Baghdad International Airport, where tests on its contents continue.

The vehicle contained fermenting tanks and dryers, such as those used to make the powder form of anthrax (search). Initial tests on the interior of the vehicle, which appeared to have been thoroughly cleaned, turned up negative results, but officials said tests were ongoing.

Officials said the equipment inside the trailer unit was scrubbed clean with a powerful, caustic cleaning agent, and some of the equipment had recently been painted. Nonetheless, the truck and its contents are still being swabbed for any trace at all of bioagents, and the samples obtained thus far have been sent to a variety of labs for analysis.

"There are a number of tests going on right now in a number of different locations in regards to Iraqi weapons of mass destruction," officials told Fox News.

The vehicle resembles an 18-wheeler Secretary of State Colin Powell (search) said in a Feb. 5 presentation before the U.N. Security Council was a mobile weapons lab that had been moved around to elude weapons inspectors.

Evidence that the vehicle was used to both manufacture banned weapons and hide them from U.N. weapons inspectors would be a boon to the United States, which has been criticized for the lack of a "smoking gun" pointing to Saddam Hussein's weapons of mass destruction.

On Feb. 5, Powell came before the U.N. in what turned out to be Washington's final large push to persuade the Security Council of the need to forcibly disarm Iraq.

Powell presented recently declassified intelligence, including satellite photos and radio intercepts, to support the U.S. case that Iraq had defied all demands that it disarm and had links to Al Qaeda and other terrorist groups.

Fox News' Bret Baier, Ian McCaleb and The Associated Press contributed to this report.