WASHINGTON (AP) – The infantry commander whose troops first captured the Iraqi weapons depot where 377 tons of explosives disappeared said Wednesday it is “very highly improbable” that someone could have trucked out so much material once U.S. forces arrived in the area.

Two major roads that pass near the sprawling Al-Qaqaa installation were filled with U.S. military traffic in the weeks after April 3, 2003, when U.S. troops first reached the area, said Col. Dave Perkins, who commanded the 2nd Brigade of the 3rd Infantry Division, the division that led the charge into Baghdad.

While he and other military officials acknowledged that some looting at the site had taken place, he said a large-scale operation to remove the explosives using multi-ton trucks would have almost certainly have been detected.

Perkins, now a staff officer at the Pentagon, was made available to reporters Wednesday by Defense Department spokesmen. He provided his account of his operations in Iraq in the middle of a furious exchange of accusations between the campaigns of President Bush and Sen. John Kerry over what happened to the missing explosives.

Larry Di Rita, the Pentagon’s top spokesman, said what ultimately happened to the explosives is unknown, although it remains under investigation by the Pentagon. But Perkins’ description seemed to point toward the possibility that the explosives were removed before the U.S.-led invasion to oust Iraqi leader Saddam Hussein, and not during the chaos afterward.

The colonel himself did not directly offer that conclusion.

But the Pentagon said a statement Wednesday, “The movement of 377 tons of heavy ordnance would have required dozens of heavy trucks and equipment moving along the same roadways as U.S. combat divisions occupied continually for weeks prior to and subsequent to the 3rd I.D.’s arrival at the facility.”

The Kerry campaign has repeatedly pointed to the missing explosives as evidence of the Bush administration’s poor handling of the war. Bush officials have responded that more than a thousand times that amount of explosives and munitions in Iraq have already been either captured or destroyed.

Kerry adviser Mike McCurry said, “From some of the Pentagon reporting today, there is a window that’s available there where either just prior to or just after the invasion, there could have been an opportunity for either Saddam to move the weapons or for something happening after that facility had been abandoned. And that is up to the administration to best determine how to answer that question when that happened. But they don’t have an answer, and that’s what we’re asking for.”

Two weeks ago, Iraqi officials told the U.N.’s International Atomic Energy Agency that the explosives vanished from the Qaqaa installation as a result of “theft and looting … due to lack of security.” The ministry’s letter said the explosives were stolen sometime after coalition forces took control of Baghdad.

The explosives were known to be housed in storage bunkers at Al-Qaqaa. U.N. nuclear inspectors placed fresh seals over the bunker doors in January 2003. The inspectors visited Al-Qaqaa for the last time on March 15, 2003, and reported that the seals were not broken; therefore, the weapons were still there at the time. The team then pulled out of the country before the invasion, which started on March 20.

According to Perkins, his 2nd Brigade arrived in the area near the Al-Qaqaa installation on April 3, 2003, part of the first large coalition combat force to come so close to Baghdad.

His troops were attacked by Iraqi forces, who were based inside the installation, he said. Al-Qaqaa had more than 80 buildings within a massive walled complex.

He estimated the enemy forces as a few hundred fighters. He sent the 3rd Battalion of the 15th Infantry to secure the base and the surrounding area, he said. A company of mechanized infantry and a mortar platoon entered the installation and defeated the Iraqi forces there.

As the rest of Perkins’ brigade moved on, the 3rd Battalion spent two days in the area, sweeping for other Iraqi forces, Perkins said. The troops didn’t specifically search for any high explosives, although they were aware that Al-Qaqaa was an important site for what was believed to be Iraq’s weapons of mass destruction programs.

Some troops found a white powdery substance on the base. But it was tested and determined it was not a chemical or biological weapon, as had been suspected, he said. Perkins did not know what it was.

Troops found other weapons, including artillery shells, on the base, he said. They didn’t specifically search for the 377 tons of high explosives, HMX and RDX, that are missing.

HMX and RDX are key components in plastic explosives, which insurgents in Iraq have used in bomb attacks. It is unclear whether the military is able to trace any of the missing explosives to specific attacks.

HMX is also a “dual use” substance powerful enough to ignite the fissile material in an atomic bomb and set off a nuclear chain reaction.

Perkins described Iraq as littered with weapons, and the Qaqaa base as one munitions depot among many. Many other depots his forces found had been cleaned out, with weapons scattered, presumably so they wouldn’t be destroyed by airstrikes.

On April 6, the battalion left for Baghdad. About four days later, another large unit, the 2nd Brigade of the 101st Airborne Division, moved into the area. That unit did not search the Qaqaa complex. A unit spokesman said there was heavy looting in the area at the time.

U.S. weapons hunters did not give the area a thorough search until May, when they visited on three occasions, starting May 8. They did not find any material or explosives that had been marked by the IAEA.