The United Nations nuclear agency has told the Security Council that nearly 350 tons of explosives is missing in Iraq and may have been stolen.

International Atomic Energy Agency Chief Mohammed ElBaradei is reporting that 342 tons of high explosives has disappeared from a site near Baghdad. IAEA officials in Vienna are quoted as saying the explosives could be used in either conventional weapons or in detonating nuclear weapons.

In a letter to the Security Council Monday, Mr. ElBaradei said Iraqi officials reported the missing explosives two weeks ago. He said the loss was likely the result of looting of an unguarded government installation.

The missing explosives were listed as 195-tons of HMX, or high-melting point explosives, 141 tons of RDX, or rapid detonation explosives and six tons of other material.

Mr. ElBaradei reported that the HMX had been under IAEA seal and the agency had verified the seal as recently as January 2003. The other explosives had been subject to regular monitoring by the IAEA of stock levels.

U.N. spokesman Fred Eckhard says this is not the first time the IAEA has reported missing explosives. "ElBaradei has repeatedly informed the Council of his concerns about material, and installations present in Iraq that have gone missing since the war last year," he said.

Pentagon officials Monday said they don't know what happened to the missing explosives, but are launching an investigation. One senior official briefing reporters suggested it would be impossible to secure the ten-thousand sites where weapons and ammunition were discovered after last year's war.

Washington's U.N. Ambassador, John Danforth, had little information about the missing weapons. But he questioned the U.N. nuclear agency's involvement in the matter, since it does not involve nuclear weapons. "We're not sure why the IAEA is seized of this (eds: is interested in this) because it's not nuclear material, but it's explosive and it's serious and we take it very seriously so we're looking into it," he said.

The explosives were reported missing from the sprawling Al-Qaqaa facility near Baghdad. The New York Times newspaper said Monday that the facility was supposed to have been under U.S. control, but is now a no man's land picked over by looters.