Human Rights Watch said Saturday it alerted the U.S. military to a cache of hundreds of high-explosive warheads in Iraq in May 2003, but that officials appeared uninterested and still had not secured the site 10 days later.

The disclosure, made by a senior official of the New York-based human rights group, raised new questions about how U.S. forces dealt with known stashes of dangerous weapons in Iraq after the invasion.

Peter Bouckaert, who heads Human Rights Watch's international emergency team, said he was shown two rooms "stacked to the roof" with surface-to-surface warheads on May 9, 2003, in a warehouse on the grounds of the 2nd Military College in Baqubah, 35 miles northeast of Baghdad. The site also included antitank and antipersonnel mines, he said.

Bouckaert said he photographed the stockpile and gave U.S. officials the exact location of the warheads, but that by the time he left the area on May 19, 2003, he had seen no U.S. forces at the site, which he said was being looted daily by armed men.

"They asked mainly about chemical or biological weapons, which we hadn't seen," he said. "I had a pretty hard time getting anyone interested in it."

Bouckaert said displaced people with whom he was working in the Baqubah area had taken him to the warheads. "They said, 'There's stocks of weapons here and we're very concerned -- can you please inform the coalition?' " he said in a telephone interview from South Africa.

"Looting was taking place by a lot of armed men with Kalashnikovs and rocket-propelled grenades," Bouckaert said. He said each of the warheads contained about 57 pounds of high explosives.

The International Atomic Energy Agency said last Monday that Iraq had reported 377 tons of high explosives missing from another site, the al Qaqaa military installation about 30 miles south of Baghdad, "due to a lack of security."

Iraqi officials told the agency that the explosives, which can be used to make the kind of car bombs that insurgents have used in numerous attacks on U.S.-led forces, disappeared after the fall of the Iraqi capital on April 9, 2003.

U.S. Army Maj. Austin Pearson said Friday that his team had removed 250 tons of plastic explosives and other munitions from al Qaqaa on April 13, 2003. But it was unclear whether those explosives were part of a cache put under seal by the U.N. nuclear watchdog agency because they could be used in the construction of nuclear weapons.

Car bombs such as those used by insurgents in Iraq require about 6.5 pounds of explosives, Human Rights Watch said.