A US Marine who was questioned last month about a once-missing teenage girl found in his barracks has now been charged in an earlier, unrelated case, according to an update from the 1st Marine Logistics Group.

The new charges are sexual assault of a minor and violating liberty restriction, the update said.

The Marine was released back to his military command after police questioned him about the formerly missing girl, 14, who was found in his barracks at Camp Pendleton in California on June 28.

The girl had been reported missing by her grandmother June 13, according to the San Diego County Sheriff's Department. The girl was returned to her grandmother.

The unnamed Marine now faces a preliminary hearing in the earlier case on Thursday at Camp Pendleton, which is between Los Angeles and San Diego.

His command will then "review all charges and evidence" to determine whether the case should be tried by court-martial.

"To protect the integrity of the ongoing investigation and the rights of the subject, further information is unavailable until this decision is made," the 1st Marine Logistics Group said.