Washington ? A U.S. Army demolition unit removed and destroyed up to 250 tons of explosives from an Iraqi storage complex shortly after the fall of Baghdad, but Pentagon officials were unable to say Friday whether the destroyed munitions were part of a cache of weaponry that U.N. inspectors said disappeared in the post-invasion chaos.

While offering a fragment of new and inconclusive evidence, Pentagon officials were unable to refute the most compelling suggestion that U.S. troops failed to safeguard the huge Al Qaqaa ammunition site: a videotape taken by a Minnesota television station showing American soldiers breaking into sealed bunkers on April 18, 2003, to find stacked crates of explosives.

The videotape appeared to show soldiers using tools to cut through wire seals left by the International Atomic Energy Agency. That bolstered reports by the interim Iraqi government and the IAEA that 377 tons of high-grade explosives were still at Al Qaqaa when the Iraq invasion began and were likely looted during the security breakdown that followed.

The munitions — primarily high-grade material known as HMX and RDX — have been a top issue in the campaign between President Bush and Democratic challenger Sen. John F. Kerry, who has charged that their theft exemplifies failures by the president in the war. Kerry has said it showed the administration failed to send in enough troops to secure Iraq and failed to heed warnings to secure the ammunition dumps.

Pentagon officials all week have tried to discredit these charges. Defense Secretary Donald H. Rumsfeld said Thursday the weapons might have been removed by Saddam Hussein’s forces in the days before the invasion.

Pentagon officials on Friday took a different tack, suggesting that large quantities of the explosives at Al Qaqaa were systematically removed and destroyed by U.S. forces after the war. At a Pentagon news conference, Army Maj. Austin Pearson said his unit removed between 200 and 250 tons of TNT, plastic explosives, detonation cords and white phosphorus rounds from the site on April 13, several days after the fall of Baghdad to American troops. Yet he could not say whether any of these were among those weapons inventoried by the IAEA.

“I did not see any IAEA seals at any of the locations we went into,” Pearson said. “I was not looking for that.”