An apparent false “active shooter” call prompted a lengthy lockdown at Redstone Arsenal in Alabama on Tuesday, but the U.S. Army post’s gates were reopened later in the afternoon.

An individual called 911 to report an “active shooter” at Building 1501, an office building known locally as “Sparkman Center Complex,” officials told Fox News. The military post in Huntsville issued the alert on Twitter for a “possible active shooter on the Arsenal” just before 10:30 a.m. The tweet continued, “Installation is on lockdown. Run, hide, fight.”

The lockdown at Redstone Arsenal was lifted around 12:30 p.m. local time and employees were allowed to “move about the post in an orderly fashion, but [were] asked to keep movements limited, as needed,” the post wrote in a Facebook post. The gates were opened but roads near the center remained closed.

Spokesman Christopher Colster said an investigation was being conducted, but officials believed there was no ongoing threat. No injuries or arrests were reported. He added a training exercise was ongoing at the post and was expected to end on Wednesday. However, Colster wouldn’t say whether the active shooter report was part of the exercise. 

“I really can’t say at this point what happened. I’m not sure myself,” Colster said. 

Army spokesman Col. Rich Spiegel initially told Fox News he could not “confirm there is an actual active shooter.”

“We are taking this seriously. There has been a very active law enforcement response,” Speigel said at the time. “There is an internal shelter in place order in effect.”

Military police, FBI agents and local officials were called to the scene. 

Employees at Redstone Arsenal were sent an email shortly after the report of an active shooter, saying the situation was “a real world event, which is not part of the exercise,” according to

“The facility is under lockdown and all gates are closed,” the email continued. 

Before the lockdown was lifted, Alabama Reps. Robert Aderholt and Mo Brooks said they were “monitoring [the] situation.” Alabama Gov. Kay Ivey said she was receiving updates on the situation and would continue to “pray for a peaceful and quick resolution.”

The U.S. Army post is located in northern Alabama, close to the Tennessee border. More than 40,000 employees work at Redstone Arsenal daily. 

It is the home to Army Material Command, other military offices and NASA’s Marshall Space Flight Center. 

A defense official said FBI and ATF agents are also based at Redstone. 

Fox News’ Jennifer Griffin, Lucas Tomlinson, Eben Brown and The Associated Press contributed to this report.