A Pentagon spokesman, Lawrence Di Rita, said Sunday evening that Saddam Hussein's government "stored weapons in mosques, schools, hospitals and countless other locations," and that the allied forces "have discovered and destroyed perhaps thousands of tons of ordnance of all types." A senior military official noted that HMX and RDX were "available around the world" and not on the nuclear nonproliferation list, even though they are used in the nuclear warheads of many nations.

The Qaqaa facility, about 30 miles south of Baghdad, was well known to American intelligence officials: Mr. Hussein made conventional warheads at the site, and the I.A.E.A. dismantled parts of his nuclear program there in the early 1990's after the Persian Gulf war in 1991. In the prelude to the 2003 invasion, Mr. Bush cited a number of other "dual use" items -- including tubes that the administration contended could be converted to use for the nuclear program -- as a justification for invading Iraq.

After the invasion, when widespread looting began in Iraq, the international weapons experts grew concerned that the Qaqaa stockpile could fall into unfriendly hands. In May, an internal I.A.E.A. memorandum warned that terrorists might be helping "themselves to the greatest explosives bonanza in history."

Earlier this month, in a letter to the I.A.E.A. in Vienna, a senior official from Iraq's Ministry of Science and Technology wrote that the stockpile disappeared after early April 2003 because of "the theft and looting of the governmental installations due to lack of security."

In an interview with The Times and "60 Minutes" in Baghdad, the minister of science and technology, Rashad M. Omar, confirmed the facts described in the letter. "Yes, they are missing," Dr. Omar said. "We don't know what happened." The I.A.E.A. says it also does not know, and has reported that machine tools that can be used for either nuclear or non-nuclear purposes have also been looted.

Dr. Omar said that after the American-led invasion, the sites containing the explosives were under the control of the Coalition Provisional Authority, an American-led entity that was the highest civilian authority in Iraq until it handed sovereignty of the country over to the interim government on June 28.

"After the collapse of the regime, our liberation, everything was under the coalition forces, under their control," Dr. Omar said. "So probably they can answer this question, what happened to the materials."