Islamic State militants do not appear to have seized any chemical weapons as they have rolled across Iraq and Syria, the Pentagon said Wednesday, as reports of U.S. troops’ exposure to chemical weapons during Washington’s last conflict in Iraq raised questions about the extremist group’s access to similar deadly agents.

“We have no indications right now that they have possession of those kinds of munitions,” Rear Adm. John Kirby, the Pentagon spokesman, told reporters.

The United States destroyed 4,530 chemical munitions following the 2003 invasion of Iraq, which was motivated in part by the George W. Bush administration’s belief that then-Iraqi leader Saddam Hussein harbored a large-scale, secret weapons program. The chemical munitions that U.S. troops later found, however, were mostly decaying remnants of a much earlier weapons program.