U.S. Air Force security guards exchanged gunfire with unknown individuals who opened fire at an entrance to Joint Base San Antonio-Lackland in Texas early Saturday morning, the Associated Press reported.

The incident, which occurred around 4:30 a.m. CST, resulted in no reported injuries, according to base officials reports.

Stefanie Antosh, public affairs chief for the base, provided details to the San Antonio Express-News. According to Antosh, the security guards returned fire at a passing vehicle at one of the base's entrances. The quick response of the security personnel highlighted the readiness of the base's defense protocols.

"We don't know what, if anything, started it," Antosh said, the AP reported. "But it wasn't an active threat to the installation, and there is no active threat to the installation."

The San Antonio Police Department (SAPD) responded promptly to the shooting and assisted in collecting evidence. Key details about the incident remain unknown at this time. The number of rounds fired during the exchange has not been determined.