The Islamic State of Iraq and Syria has seized a facility that produced chemical weapons under Saddam Hussein, but the site includes old and contaminated chemical weapons that U.S. officials said would be ineffective and hard to move.

Officials told the Wall Street Journal the weapons at the Al Muthanna complex are also hard to relocate, further complicating any effort by ISIS to use them in its offensive against Iraqi security forces.

Despite confidence that ISIS won’t be able to make the chemical weapons operational, the U.S. remains “concerned about the seizure of any military site" by ISIS, State Department spokeswoman Jen Psaki told the paper. "We do not believe that the complex contains materials of military value, and it would be very difficult, if not impossible to safely move the materials."

While the Al Muthanna complex was bombed during the first Iraq war in 1991 and most of the facility was destroyed under the watch of the United Nations in the early 1990s, some chemical weapons and chemicals used to make the weapons remained, according to a CIA report on Iraq's weapons of mass destruction.  

Shortly after Saddam took power, he made chemical weapons a top priority as Iraq was soon to engage in a war with Iran. Mustard gas and the nerve agents tabun and sarin were made there, along with other chemicals.