An official familiar with the report said US army staged raids in Baghdad in March, uncovering evidence that someone was attempting to produce ricin, a potentially deadly toxin made from castor beans.

"We conducted a lot of raids, and developed information over the next two or three months," the official said.

They found "active efforts by anti-coalition forces to create chemical weapons."

"They were trying to find people who knew something about chemical weapons, and to get them to produce some. They tried to put some in mortar rounds," he said, adding that ricin and other agents were used.

"I think this is a case where we got ahead of a problem a bit," he said.

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