CHAMBERSBURG, PA — One person who has injured in an explosion at the Letterkenny Army Depot in Chambersburg has died, depot officials said Friday.

“It is with a heavy heart that I announce the passing of dedicated member of our LEAD family who was injured in Thursday’s explosion,” Depot Commander Col. Stephen Ledbetter said in a press release.

Officials said on Thursday that four people were injured and three of the victims had to be airlifted to the hospital. Two people remain in the hospital in critical but stable condition. The third victim was treated for smoke inhalation and released the same day.

The employees were injured in an explosion that was followed by a subsequent fire. The explosion happened around 7:20 a.m. Thursday in a production facility at the depot.

“The entire Letterkenny family is mourning this loss,” Col. Ledbetter said. “We continue to keep the families and all of our teammates in our hearts and prayers.”

Chaplains and counselors are at the depot to provide support.

The incident is being investigated by Letterkenny’s safety and engineering offices, OSHA and the depot’s fire and emergency services.

The depot, located 160 miles (257 kilometers) west of Philadelphia, or about 55 miles (88 kilometers) southwest of Harrisburg, employs about 3,600 people. The depot’s website says work there focuses on air defense tactical missile ground support equipment, mobile electric power generation equipment, Patriot missile recertification and route guidance vehicles.

Reporting from The Associated Press was used in this report.

Photo by Markell DeLoatch/Public Opinion via Associated Press