"Our feeling at this point is that had this stuff been mixed and used, it could have been very easily used against Iraqi and coalition forces," Boylan said.

The military cautioned in a statement, however, that ongoing testing at the facility was "insufficient to determine what the insurgents had been producing" and that further tests were required.

U.S. troops, acting on a tip from detainees under interrogation, raided the building Tuesday, the statement said. The military did not say if anyone was detained in the raid and said it was investigating which insurgent group was operating the facility.

The military has found many suspected chemical sites in the past, none of which ended up containing chemical or biological weapons. Testing of such sites can take several days.

Boylan said the materials did not appear to be linked to Saddam Hussein's ousted regime.

The U.S. invaded Iraq in March 2003 to destroy Saddam's purported unconventional weapons of mass destruction. None were ever found.

U.S. arms investigators have said there was evidence that Iraqi resistance groups had tried to manufacture chemical weapons. The information was disclosed in the final report of Charles A. Duelfer's Iraq Survey Group, the account of its fruitless 18-month hunt for weapons of mass destruction in Iraq.

In an annex to the Duelfer report, the joint CIA-Pentagon teams told of having broken up an insurgent group in June 2004 that for six months tried to make weapons agents.

The group had recruited a Baghdad chemist and obtained chemicals from farmers who looted state companies and from shops in Baghdad's chemicals market, the report said. They first tried to make tabun, a nerve agent, but could not get the ingredients. Then the chemist, who had no weapons-making experience, was unable to manufacture the blistering agent mustard, although he had the right chemicals, the report said.

The insurgents hired another chemist, who succeeded in making ricin base, a poisonous plant extract from castor beans, but at that point a U.S. raid on the laboratory, at Baghdad's al-Abud trading complex, disrupted the network.

The Duelfer account also said various sources reported insurgents were trying to produce chemical weapons elsewhere in Iraq.

In November, U.S. and Iraqi forces that overran Fallujah reported finding an insurgent lab which included the poisonous industrial compound hydrogen cyanide and a book of instructions for making potential chemical weapons.

Weeks earlier, Jordanian authorities said they had foiled planned chemical attacks by suicide bombers on Jordanian government targets. They said the plot was conceived by Abu-Musab al-Zarqawi, leader of the al-Qaida wing in Iraq.

© 2005 Associated Press.

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