The Pentagon reported yesterday that U.S. Army soldiers removed about 250 tons of material from the Qaqaa munitions complex in April 2003, the first time defense officials have credited U.S. forces with carting away a large amount of explosives from the Iraqi site for destruction.

But the Army major who commanded the operation told reporters he could not say whether any of the munitions were part of the 377 tons at the center of a political firestorm this week between the campaigns of President Bush and Sen. John F. Kerry.

The officer, Maj. Austin Pearson, said some of the material taken from storage bunkers at the sprawling installation included "plastic explosives." But he said he saw no closed bunkers or seals of the kind that the International Atomic Energy Agency had put on the bunkers containing HMX, one of the explosives in the disputed group.

Pearson's appearance at a Pentagon news conference represented the latest effort by the Bush administration to defend its work to secure Iraq's vast stockpiles of munitions after last year's invasion. Kerry has seized on the disappearance of the 377 tons, which the IAEA announced Monday, to further his argument that Bush has mismanaged military operations in Iraq.

Each day this week has produced new disclosures and statements -- by international weapons experts, government officials, journalists and others -- attempting to shed light on what might have become of the missing explosives. Increasingly, evidence has pointed to the conclusion that some or all of the material was looted after the fall of Baghdad on April 9, 2003.

One of the strongest indications that the disputed explosives were still at the site in mid-April comes from a videotape shot April 18 by a crew from KSTP-TV of Minneapolis-St. Paul and aired nationally Thursday by ABC. It showed two soldiers from the 101st Airborne Division, whose unit had camped near Qaqaa, checking out sealed bunkers at the complex. Entering the buildings, they discovered crates with what appeared to be IAEA labeling.

According to the TV crew, the soldiers did not remove the explosives, and left the bunkers open and unguarded when they rejoined their unit. A source with firsthand knowledge of IAEA activities in Iraq said yesterday that the seal in the videotape "looks similar if not identical" to that used by the IAEA.

Nevertheless, Pentagon officials yesterday continued to hold open the possibility that the explosives were taken by Iraqi authorities after the departure of IAEA inspectors in mid-March and before the arrival at Qaqaa of the first U.S. troops in early April. Pentagon spokesman Lawrence T. Di Rita stood beside Pearson yesterday and spoke of "some apparent movement of heavy equipment" at the munitions complex in that period.

On Thursday, the Pentagon released an aerial reconnaissance photo dated March 17 showing two big trucks in front of two bunkers, although what the bunkers contained was not specified. Di Rita said yesterday that other photos show "a significant number of large trucks on that site near those bunkers," but these pictures remain classified, he said, "because we don't understand them well enough."

Pearson's operation occurred on April 13. As commander of the 24th Ordnance Company, Pearson and his team were to find any "exposed" Iraqi ammunition caches that posed a threat to U.S. forces and dispose of the munitions. The unit was attached to the 3rd Infantry Division, which led the Army advance on Baghdad and reached Qaqaa on April 3.

Pearson said the material his unit carted away included plastic explosives, TNT, detonation cords and white phosphorous rounds. Di Rita asserted at the outset of the news conference that some of the removed material included a portion of the RDX -- a key ingredient in some plastic explosives -- that is among the missing substances. Pearson stopped short of making such a link.

"I did not see any IAEA seals at the locations that we went into," Pearson said. "I was not looking for that. My mission specifically was to go in there and to prevent the exposure of U.S. forces and to minimize that by taking out what was easily accessible."

Unlike the HMX, which had been stored in sealed bunkers because of its potential use to trigger nuclear devices, the RDX was not.

The IAEA has been criticized by Bush administration officials for publicizing the loss of the high-grade explosives so close to the U.S. presidential election. In an interview yesterday, Mohamed ElBaradei, the IAEA's director general, said he had not intended to influence the election. He said the Iraqi interim government, which reported the explosives lost in an Oct. 10 letter to the IAEA, is responsible for bringing the issue to the public's attention.

ElBaradei, a former Egyptian diplomat, said he passed the information to U.S. authorities five days later, hoping they could help retrieve the explosives. He withheld the information from the U.N. Security Council until the New York Times, working with CBS News, broke the story on Monday.

"The whole thing was driven by the Iraqi letter," he said.

ElBaradei's relations with the Bush administration have been tense since he challenged U.S. claims that Iraq had made significant advances in developing a nuclear bomb before the war. The administration opposes ElBaradei's bid for a third term as IAEA chief.

Lynch reported from the United Nations.

Army Maj. Austin Pearson and his team were to dispose of any "exposed" ammunition caches in spring 2003.