WAYNOKA, Okla. (AP) — Two Oklahoma firefighters were among four people killed early Friday in a house fire in northwestern Oklahoma, a fire official said.

Assistant Oklahoma State Fire Marshal James Fullingim said the blaze was reported just after 3 a.m. Friday in Waynoka, about 110 miles (180 kilometers) northwest of Oklahoma City.

The fire was reported by a person reportedly trapped in a bedroom of the home, Fullingim said, and two firefighters who arrived at the scene entered the home and found a man and woman in the bedroom.

The four died as the firefighters tried to remove the occupants from the home.

“We don’t know exactly what happened,” Fullingim said. “One firefighter was trying to locate an exit route out of the house.”

The names of the four were not immediately released. Fullingim said both firefighters were male and the two inside the home were a male and a female.

The cause of the fire has not been determined, Fullingim said.