The Army’s Redstone Arsenal in Alabama was locked down for more than two hours Tuesday amid reports of a possible active shooter.

“Possible active shooter on the Arsenal. Installation is locked down. Run hide fight,” the arsenal tweeted at about 11:30 a.m. ET.

No shootings or injuries were immediately reported, and much of the sprawling base reopened early in the afternoon.

Redstone Arsenal covers almost eight square miles adjacent to the city of Huntsville and on most weekdays has more than 30,000 workers on site. All gates were closed when the incident was reported, and employees sheltered in place.

Spokesman Christopher Colster said there initially was confusion about whether it might be part of a massive drill schedule for Wednesday.

“My first thought was that it was part of the drill,” he said. But he said it was soon confirmed that the incident was unrelated to the drill. A section of the base near where the incident was reported remained closed after some gates opened.

“Our thoughts and prayers are with everybody on the arsenal grounds,” Colster said. “We are hoping to hear there are no casualties.”

The Army Materiel Command, Aviation and Missile Command and Missile Defense Agency are housed on the base. The Marshall Space Flight Center, the government’s civilian rocketry and spacecraft propulsion research center, also is located on grounds and was in lockdown as well.

Taylor Reed, a Huntsville native who works for the Missile Defense Agency, sheltered in place in a complex near where the possible shooter was reported.

“We had an ‘all hands’ with the three star general, or new director, when an alarm started going off. He was, like, is that a fire alarm? Are we ok?” Reed said, adding that an army…