June 27 (UPI) -- The Redstone Arsenal U.S. Army installation in Huntsville, Ala., ended a two-hour lockdown Tuesday after reports of a possible shooter were unfounded.
An "all clear" was declared at 12:27 p.m..
Chris Colster, spokesman at the arsenal, said gates reopened but asked for "prayers for those involved in this situation."
"We do not believe there is a threat or we would not have opened the installation back up," Colster said.
The Arsenal received two calls made to 911 about a possible shooter at the Sparkman Center, the headquarters for the Army's Aviation and Missile Command. They reported hearing shots fired and one said a weapon was seen.
Col. Tom Holliday, Garrison Commander at Redstone Arsenal, said at a news conference there was no active shooter.
Sparkman Center remained restricted until 3 p.m. CNN reported the incident was on Building 5301's second floor.
Holliday said medical calls involved people evacuated from the building, including heat issues.
"What I really want to make clear when it comes to the safety of our work force, our systems worked," Holliday said. "That was proven today."
Holliday said he does not believe officials overreacted to the 911 calls.
The arsenal had posted on Twitter: "Possible active shooter on the Arsenal. Installation is locked down. Run hide fight."
"This is a real world event, which is not part of the exercise. The facility is under lockdown and all gates are closed, More to follow," read an email to employees, sent at 10:31 a.m.
Redstone Arsenal has more than 40,000 employees at the 30,000-acre facility. About 1,500 of them are uniformed personnel.
The arsenal had planned active shooter training, but Redstone officials said Tuesday's lockdown was not a drill.
Redstone also is home to Army Materiel Command, Marshall Space Flight Center, Bureau of Alcohol, Tobacco, Firearms and Explosives and FBI facilities.