Passengers of a Southwest Airlines flight made an emergency exit after a smartphone battery of a co-traveller caught fire and damaged a seat in the US state of Denver.

Southwest Airlines Flight 3316, scheduled to head to Houston, was still at the gate at Denver International Airport when the cellphone battery of one of the 108 passengers on board started a fire, a spokesperson for the airline told USA TODAY.

Passengers, who were sitting in the back of the plane, used the rear emergency slides to exit the flight.

Those who were sitting in the front door escaped the flight from the front door.

The flight crew managed to extinguish a seat that caught fire due to the burning cell phone, the airline told USA Today.

Preliminary reports suggested one passenger was injured during the evacuation process.

The passengers, whose phone caught fire, underwent treatment for burn injury.

"Southwest’s Customer Care Team is working to accommodate the passengers on another aircraft to their original destination of Houston," the airline told USA Today.

"Nothing is more important to Southwest than the safety of its customers and employees," the airline said.