HUNTSVILLE, Ala. -- Authorities locked down an Alabama military post on Tuesday amid reports of possible active shooter, and workers were advised to "run hide fight." About two hours later, the all clear was given and officials said there were no confirmed injuries or arrests.A safety drill was planned for Wednesday, but Redstone Arsenal spokesman Christopher Colster said he wasn't sure "at this point what happened" at the base near Huntsville. He said there would be an investigation."We do not believe there is a threat or we would not have opened the installation back up," he said.Earlier, Colster had said the report of a shooter was not part of any exercise. In a tweet announcing the possible shooter, the base said: "Possible active shooter on the Arsenal. Installation is locked down. Run hide fight."Police cars with flashing lights blocked entrances to Redstone, which also has facilities used by federal law enforcement agencies. Images on social media showed an ambulance and what appeared to be civilians standing outside the Sparkman Center, which includes multiple buildings with offices, an auditorium, cafeteria and an interior courtyard.But Huntsville hospital officials said they had not heard of any incoming patients, local TV stations reported.Alabama Gov. Kay Ivey's office said it couldn't provide any details."My office is aware of the developing situation at Redstone Arsenal, and we are monitoring it closely. I am praying for a swift resolution to this matter," she said in a statement.More than 30,000 government employees, civilians and contractors work daily at Redstone. It is home to Army missile defense programs and other military offices.NASA's Marshall Space Flight Center, which oversees rocket propulsion operations, also is located at Redstone.----------