Early results of an investigation into a Baghdad (search) explosion that killed two members of a U.S. team looking for weapons of mass destruction indicate the blast was accidental, a U.S. official said Tuesday.

But a defense official in Baghdad said Tuesday that the team might have been was lured into a trap when a building they were searching exploded.

The Iraq Survey Group (search) team, which reports to the CIA (search), was searching the building Monday after a tip that the site may have been producing chemical weapons, the defense official said.

The U.S. official, speaking in Washington, said it appears that members of the group accidentally touched off a fire as they tried to enter the building. The fire may have caused a second explosion outside the building.

The chemicals were standard industrial chemicals, stored in an improper or unsafe way in the building, the official said from Washington. There was no ambush, nor was anyone lured into the building, the U.S. official said.

The defense official said investigators were trying to determine whether the team was given a false tip intended to lure them into a trap.

Both the U.S. official and the defense official spoke on condition of anonymity.

The Iraq Survey Group, made up of dozens of teams, has been conducting a secretive and largely fruitless weapons hunt across Iraq for more than a year. The survey group combines members of the Central Intelligence Agency, Defense Intelligence Agency, U.S. military Special Forces and others.

The explosion leveled the building, killing the two and wounding five. After the blast, cheering Iraqis swarmed over the team's burned-out Humvees, beating them with sticks and waving looted weapons.

A U.S. soldier was seen being taken away on a stretcher, her chest and face severely burned. Several Iraqis were pulled out of the wreckage, including a woman who wept as she was carried over a man's shoulder to safety.

In Baghdad, Brig. Gen. Mark Kimmitt did not say what sort of chemical munitions were believed to be produced at the site.

"Chemical munitions could mean any number of things," including smoke grenades, he said.

In October 2002, Bush said Iraq had "a massive stockpile of biological weapons that has never been accounted for and is capable of killing millions."

In his television address two days before launching the invasion, Bush said. U.S. troops would enter Iraq "to eliminate weapons of mass destruction," or WMD.

With no success finding that alleged stockpile, some of the Iraq Survey Group teams have been redirected to hunting fugitives from Saddam Hussein's regime and foreign terrorists believed to be launching attacks in Iraq, military officials have said.