The strongest evidence to date indicates that conventional explosives missing from Iraq's Al-Qaqaa installation disappeared after the United States had taken control of Iraq.
Barrels inside the Al-Qaqaa facility appear on videotape shot by ABC television affiliate KSTP of St. Paul, Minn., which had a crew embedded with the 101st Airborne Division when it passed through Al-Qaqaa on April 18, 2003 -- nine days after Baghdad fell.
Experts who have studied the images say the barrels on the tape contain the high explosive HMX, and the universal markings on the barrels are clear that these are highly dangerous explosives.
"I talked to a former inspector who's a colleague of mine, and he confirmed that, indeed, these pictures look just like what he remembers seeing inside those bunkers," said David Albright, president of the Institute for Science and International Security in Washington.
The barrels were found inside sealed bunkers, which American soldiers are seen on the videotape cutting through. Inspectors from the International Atomic Energy Agency sealed the bunkers where the explosives were kept just before the war began.
"The seal's critical," Albright said. "The fact that there's a photo of what looks like an IAEA seal means that what's behind those doors is HMX. They only sealed bunkers that had HMX in them."
After the bunkers were opened, the 101st was not ordered to secure the facility. A senior officer told ABC News the division would not have had nearly enough soldiers to do so.
It remains unclear how much HMX was at the facility, but what does seem clear is that the U.S. military opened the bunkers at Al-Qaqaa and left them unguarded. Since then, the material has disappeared
Pentagon spokesman Larry DiRita said it's not clear what the photos indicate.
"We know there were other units in the area who acknowledged finding explosives," he said. "Some Explosive Ordnance Destruction units have a recollection that some high explosives in the area were taken out of there."
DiRita said the Pentagon is trying to contact the units of the 101st Airborne Division that may have been involved in the opening of these bunkers to get a better sense of what happened.
Late today, the Pentagon released a satellite image of Al-Qaqaa bunkers taken March 17, 2003, that shows the presence of two heavy-lift tractor trailers outside of a bunker. The Pentagon is uncertain about whether the specific bunker where the trucks are located actually contained explosives that are now missing.
Their intent in releasing the image is to demonstrate that on the same day that the IAEA inspectors left Iraq, Saddam Hussein's regime was in control of the facility, countering the impression that this was a "hermetically sealed" location and showing that access was available to non-U.N. personnel.
Not released today were images taken March 14, 2003, and March 20, 2003, that show no vehicles on the premises. There also was an image from April 1, 2003, that showed a large number of trucks at the nearby Iskandariyah airfield. Officials acknowledged they have no idea what those trucks were there for.
It is highly unusual for the Pentagon to release spy satellite imagery. Officials said today's decision was made with the full agreement of the intelligence community and that the White House did not have to approve the release.
ABC News' Martha Raddatz filed this report for World News Tonight. Luis Martinez contributed to this report.