Four people were injured and taken to area hospitals after a small explosion Thursday at Letterkenny Army Depot in southern Pennsylvania, according to the depot's Facebook page.
The blast erupted around 7:20 a.m. ET in the paint shop of a large warehouse and sparked a fire, Letterkenny said. The warehouse had to be evacuated, emergency officials said.
At least three of the injured were airlifted to hospitals, according to the depot. It said all employees had been accounted for.
The injured were burn victims, the Franklin County Fire Company said.
"The safety and well-being of our employees is our top priority," said Col. Stephen Ledbetter, commander of the Letterkenny Army Depot, adding "the injured employees and their families are in our thoughts and prayers."
"An apparent explosion resulting in a fire occurred in Bldg. 350 at Letterkenny Army Depot. The fire was contained and we have 100 percent accountability of our workforce," the depot said on Facebook. The families of the injured have been notified.
In earlier posts on its Facebook page that were later removed, the depot urged employees to remain in their work area and not to enter the depot. It also asked them not to share information about the explosion on social media.
Another now-deleted post said, "There is no suspicion of terrorist activity."
Letterkenny said, "We are conducting an investigation into the cause of the incident, so we know exactly what happened."
Letterkenny Army Depot is just outside Chambersburg, about 100 miles north of Washington. The 18,000-acre base employs 3,600 civilians, contractors and military personnel.
It was selected in 1941 as an ordnance depot. Today, it provides support for US and allied air and missile defense forces.
"Letterkenny Army Depot develops and delivers materiel readiness for Air Defense forces of the United States and its international partners and builds combat power for combined and joint route clearance operations worldwide," the depot's website says, describing its mission.