Pentagon officials have told Fox News that American-made stinger missiles are likely in the hands of insurgents in Iraq.

The ISIS fighters most likely procured the missiles while overrunning military bases.

As the U.S. weighs its options, the Pentagon is sending 150 Marines to reinforce the American embassy in Baghdad.

Read more below from FoxNews.com:

The Stinger missile is a shoulder-fired surface-to-air weapon that is used against aircraft.

As ISIS forces have advanced through Iraq, concerns have increased that more U.S.-made weaponry could fall into the hands of the radical group.

Iraqi intelligence officials said ISIS fighters managed to take control of two big weapons depots late last week holding some 400,000 items, including AK-47 rifles, rockets and rocket-propelled grenades, artillery shells and mortars. A quarter of the stockpiles were quickly sent to Syria in order to help the group's comrades there, they said.

Also last week, according to a report from the West Point Combating Terrorism Center, the ISIS "now possesses scores of Iraqi military equipment originally provided by the United States, from Humvees and cargo vehicles to small arms.”