Some controversy also exists regarding whether the invasion increased or decreased the potential for nuclear proliferation. For example, hundreds of tons of dual-use high explosives that could be used to detonate fissile material in a nuclear weapon were sealed by the IAEA at the Al Qa'qaa site in January 2003. Immediately before the invasion, UN Inspectors had checked the locked bunker doors, but not the actual contents; the bunkers also had large ventilation shafts that were not sealed. By October, the material was no longer present. The IAEA expressed concerns that the material might have been looted after the invasion, posing a nuclear proliferation threat. The US released satellite photographs from March 17, showing trucks at the site large enough to remove substantial amounts of material before US forces reached the area in April. Ultimately, Major Austin Pearson of Task Force Bullet, a task force charged with securing and destroying Iraqi ammunition after the invasion, stated that the task force had removed about 250 tons of material from the site and had detonated it or used it to detonate other munitions. Similar concerns were raised about other dual use materials, such as high strength aluminum; before the invasion, the US cited them as evidence for an Iraqi nuclear weapons program, while the IAEA was satisfied that they were being used for permitted industrial uses; after the war, the IAEA emphasized the proliferation concern, while the Duelfer report mentioned the material's use as scrap. Possible chemical weapons laboratories have also been found which were built subsequent to the 2003 invasion, apparently by insurgent forces.