ATLANTA (AP) — Two workers were killed and Johnathan Walkeranother injured in an explosion early Tuesday at a Delta Air Lines maintenance facility near the Atlanta airport.

Delta said it was working with local authorities to investigate what happened.

WSB-TV reported that a tire on a plane exploded, killing one Delta employee and a contract worker. The television station cited unnamed sources.

Several Atlanta fire units and police responded to the maintenance hangar near Hartsfield-Jackson Atlanta International Airport shortly after 5 a.m., The Atlanta Journal-Constitution reported.

“The Delta family is heartbroken at the loss of two team members and the injury of another following an incident this morning at the Atlanta Technical Operations Maintenance facility,” Delta said in a statement. “We have extended our full support to family members and colleagues during this incredibly difficult time.”

Delta thanked first responders and medical teams.

“We are now working with local authorities and conducting a full investigation to determine what happened,” the Atlanta-based airline said.