Story highlights Investigators are looking at why there were 911 calls at Army's Redstone Arsenal post

The base in northern Alabama was locked down for several hours

(CNN) Part of the US Army's Redstone Arsenal post in northern Alabama was locked down for hours Tuesday as authorities investigated reports that a shooter was in one of the buildings.

But the lockdown was lifted late Tuesday afternoon when investigators determined those reports were unfounded, Garrison Commander Col. Thomas Holliday Jr. said at a news conference. The 911 calls were "not credible information," he said.

Holliday said 911 received two calls from the Sparkman Center around 9 a.m., one saying shots were fired and the other saying someone saw a weapon.

Possible active shooter on the Arsenal. Installation is locked down. Run hide fight. — Redstone Arsenal (@TeamREDSTONE) June 27, 2017

at the Sparkman Center complex. At first much of the sprawling military base was locked down. An Army email sent to facility personnel and relatives shortly after 10 a.m. Tuesday said an active shooter was reported on the second floor of Building 5301, the Aviation and Missile Command buildingat the Sparkman Center complex.

By 1 p.m., the lockdown had been lifted except for the Sparkman Center. Holliday said it took hours to clear that building because of its size -- about 1.5 million square feet -- and the number of people who work there.

Read More