Explosion at Pennsylvania Army depot injures 4

July 19 (UPI) -- An explosion Thursday at Letterkenny Army Depot in south-central Pennsylvania sent four people to the hospital, officials said.

Depot commander Col. Steven Ledbetter told Fox News the small explosion and fire happened in a paint area, injuring four people.

The Franklin Fire Company said on its Facebook page three were taken to the hospital via air ambulance. They were taken in serious condition and another person was taken to Chambersburg Hospital in an unknown condition.

Letterkenny Army Depot in Chambersburg had warned employees about the explosion via messages on Twitter, which were later removed.

The blast occurred in a vehicle maintenance building the size of several football fields and usually has several hundred employees working inside -- the majority are civilian workers or civilian contractors.

Letterkenny, which opened 23 days after the attack on Pearl Harbor, is the largest employer in the county and spans over 17,500 acres. The Army uses the depot to refurbish missile defense systems.