Ohio’s Wright-Patterson Air Force Base was put on lockdown Thursday night to investigate reports of a shooter on the campus, according to the airbase.

Stacey Geiger, spokeswoman for the base, said a report of an active shooter came in at 9:25 p.m. Shortly before midnight, Geiger told The Associated Press that emergency responders were doing a second sweep of the grounds.

At 12:45 a.m., the base tweeted that security was still conducting a sweep of the National Air and Space Intelligence Center. The center is the Department of Defense's primary source for foreign air and space threat analysis, according to its website. More than 4,100 military, civilian, reserve, guard and contract employees make up the global personnel of NASIC, headquartered at the base, near Dayton

The base said in an earlier tweet that “All of our military and civilian employees are trained to quickly assess the situation and take appropriate action.”

The lockdown was announced multiple times over loudspeakers at the base. It is unknown whether any shots were fired.

Spokespeople said they would provide more information when it's available. A media briefing was expected.