Update

Crews have been dispatched to Letterkenny Army Depot for a report of an explosion.

An explosion occurred at around 7:15 a.m. Thursday in the 300 block of California Avenue, FOX43 reports.

Injuries have been reported as a result of the incident, but it is not currently known how many people were injured or how severe the injuries are.

WGAL reports multiple medical helicopters have been dispatched to the scene, and staff members are being asked to stay in their work areas until further notice.