PONDERAY — A family of five and a Chihuahua escaped serious injury after being trapped inside their apartment by a fire burning outside their door on Sunday night.

The family, two adults and three children, were taken to Bonner General Hospital for treatment for smoke inhalation and later released, Northside Fire District and Ponderay Police officials said on Monday.

The family’s identity was not released.

The fire broke out in the outdoor stairwell landing on the building’s third floor shortly after 10:30 p.m. The landing provided access two third-floor apartments, only one of which was occupied at the time.

Firefighters from Northside knocked down the flames on the landing so the family could be evacuated. Police and sheriff’s deputies went door-to-door in the 15-unit building to evacuate the other residents.

The cause of the fire was undetermined on Monday, Northside Assistant Chief Robert McArthur. Arson was ruled out, however.

There were murmurs around the complex that it may have started because of a carelessly discarded cigarette, although Northside officials declined to confirm or deny those reports.

Smoke from the fire activated a smoke detector in the trapped family’s apartment. They stayed on the phone with Bonner Dispatch until they were freed by firefighters, said Northside Chief Brad Mitton.

Mitton said sheriff’s deputies used a fire extinguisher mounted in the stairwell to make an initial attack.

“Quick thinking and quick reaction from law enforcement helped us a whole bunch,” said Mitton.

A ladder truck from Sandpoint and an ambulance from Sagle were brought to the scene. Officials from Bonner County Emergency Management and Red Cross were also on hand.

A first-floor tenant, Kimberly Roberts, said she did not hear the smoke detector two flights up and learned there was trouble only when law enforcement began banging on doors to evacuate residents.

“We had no idea there was a fire going on two stories up,” said Roberts.

Northside Fire officials said the building’s smoke detectors work independently of one another.

The fire was confined to the stairwell and did not enter the third-floor apartment, although the dwelling did suffer some smoke damage.

Mitton said teamwork among the responders was a crucial element during the blaze.