U.S. Air Force security guards exchanged gunfire with unidentified individuals who opened fire at the entrance of Joint Base San Antonio-Lackland in Texas early Saturday morning.

The incident, which occurred around 4:30 a.m. CST, resulted in no injuries. Security personnel returned fire at a passing vehicle, but the motive and details of the attack remain unclear.

The San Antonio Police Department is leading the investigation. The base temporarily closed the entrance for investigation but was not put under lockdown, Newsweek has reported.

Base officials confirmed there is no ongoing threat, and operations have resumed as normal.

Written by B.C. Begley