OKLAHOMA CITY -- Oklahoma City fire investigators are working to determine what caused a fire at the Pinehurst Apartments near N.W. 122nd Street and MacArthur Boulevard.

Firefighters arrived to find residents alerting their neighbors of the blaze. Firefighters said flames spread quickly due to people leaving their apartment doors open, which gave the fire plenty of oxygen to accelerate.

At least eight units are damaged and part of the roof collapsed.

The Red Cross is helping about a dozen displaced families.

One firefighter received treatment for a shoulder injury. No other injuries were reported.