Two adults were taken to hospitals with burns and smoke inhalation on Sunday, after a fire involving a damaged home on the eastern end of St. John's.
St John's Regional Fire Department staff and Royal Newfoundland Constabulary were called around 1:30 am at a home on Newfoundland Drive.
Acting Platoon Chief Paul Grandy told CBC the damage is serious.
A family living in the basement apartment is also without home, even if they were not injured, Grandy said.
He said when the crew arrived, two people were outside the home.
RNC has held the stage and an investigation is underway.
The Red Cross said in a statement Sunday that volunteers have arranged "emergency, food and clothing purchases" for the couple and their 15-year-old daughter who lived in the basement apartment.
Similar help can be provided for the two people who were hospitalized as needed, the Red Cross said.
It is not yet known where the fire began.
Read more from CBC Newfoundland and Labrador