One person is dead and another is in critical condition in hospital after an early morning fire at a south-Ottawa highrise apartment building.

More than a dozen residents -- mostly senior -- were treated at the scene for smoke inhalation. A total of four people were sent to hospital.

The fire has left an estimated 30 people homeless on Christmas Eve, according to the Red Cross. However, all of the displaced residents have found temporary accommodation, mostly with family.

Fire officials say the fire broke out in an end-unit apartment on the second floor of a highrise apartment complex at 1695 Playfair Ave. in the Alta Vista area. Once ignited, the fire spread quickly to other parts of the building.

Firefighters received the call shortly before 5 a.m. Fifty-eight firefighters responded to the scene.

Police say the cause of the fire remains unknown. The Ontario Fire Marshal's office has been called in to investigate.

Arson has not been ruled out.