The security forces personnel who wrongly allowed a possible kidnapper and his alleged victim past the main gate of Nellis Air Force Base in Nevada early Tuesday morning have been placed on administrative duty.

In a statement Thursday evening, Nellis spokeswoman Rebekah Mattes said that the preliminary findings of an investigation into the breach found that “proper entry procedures were not followed” when the two were allowed on base together in a white van at 4:25 a.m. that day.

Mattes said it appears to be an isolated incident, but more information will be available after the investigation is finished.

“Security forces personnel at the gate during the time of entry have been placed on administrative duties pending the outcome of the investigation,” Mattes said.

The alleged victim, a civilian woman, approached airmen that morning and told them she had been kidnapped and sexually assaulted. The airmen called it in at about 5 a.m., and security forces found the alleged assailant — also a civilian — and the vehicle in the parking lot of the Crosswinds dining facility on base at about 5:30. Las Vegas police took over the investigation of the alleged kidnapping and sexual assault, and Nellis began investigating how the breach happened.

“The 99th Air Base Wing takes installation security very seriously and is looking into the matter and examining what processes may need to change to further bolster security,” Mattes said Wednesday evening. “At no point were aircraft, classified information or personnel threatened.”