WASHINGTON (AP) -- The State Department says the Libyan government is holding four U.S. military personnel, but details of their detention remain unknown.

State Department spokeswoman Jen Psaki says officials are trying to determine what occurred.

Psaki said Friday night that the United States is in touch with Libyan officials to ensure the Americans' release.

The U.S Embassy in Tripoli includes a security detail. The embassy's personnel are restricted in their movements in Libya.