Fire investigators are trying to determine what caused a large blaze in Saint John Friday afternoon.

The flames gutted two apartments on Victoria Street, leaving seven people homeless.

The blaze started in a vacant building, then quickly spread to an apartment building next door. Two dozen firefighters were on the scene for hours trying to contain the fire.

Flames were shooting from the rooftops as thick, black smoke billowed from the building.

"The residents whose home was burning in front of them, it was a very emotional time," said Bill Lawlor of the Canadian Red Cross.

"We certainly encouraged them to try to come with us and perhaps even come to the hotel at that point in time just to get away from the scene. But they were standing there, just staring at the apartment building as it was slowly being destroyed."

Fire investigators spent Saturday morning searching for clues in the rubble. The District Fire Chief told CBC that arson is a possible cause.

'It was clear to us the tenants would not be returning at all to that location'—Bill Lawlor, Canadian Red Cross

The Saint John Fire Service said one tenant was taken to hospital to be treated for smoke inhalation.

Lawlor said they were fortunate the fire didn't spread to nearby buildings.

"The flames were very, very strong. It was clear to us the tenants would not be returning at all to that location."

Housing Alternatives Incorporated owns the building. The five adults and two children who lived in the apartments are now receiving help from the Red Cross.

Lawlor said the organization will provide accommodations and food for three days while the damage is assessed. The organization will co-ordinate with the Salvation Army if the tenants need long term help.

The Saint John Police major crime unit is also investigating the fire.