Fire investigators are still trying to determine what caused a blaze at an apartment building in Amherst, N.S. Monday evening.

The fire started around 8:30 p.m. on Dickey Street, forcing 28 tenants to flee the building.

Brandon Collins, 10, was visiting his grandmother when they heard an alarm in the hallway. The pair immediately sprang into action.

“I went out and there was a guy lying down and he kept saying ‘call 911, call 911’,” says Collins.

“I went and hollered and said there was a fire and for them to get out,” says resident Audrey Richard.

Thanks in part to Collins’ 911 call and his grandmother’s yelling in the hallways, 28 tenants in the 16 apartment units managed to escape the fire without injury.

Collins’ pet hamster also escaped the blaze unharmed.

“I thought he would be dead,” says Collins.

Most of the residents were able to stay with family and friends overnight but eight tenants ended up at the fire department in an emergency shelter set up by the Red Canadian Red Cross.

“We’re continuing to assess the needs of the people to see what clothing, shelter, food, medications they may require,” says Mike Johnson, a volunteer with the Canadian Red Cross.

Investigators say the fire started in the bedroom of one apartment but the cause remains undetermined.

“The damage, I would describe it as mostly to one apartment,” says Amherst Fire Chief Greg Jones. “There is some damage throughout the building, however, the majority of it is in that one apartment.”

Officials are hoping to allow tenants back into the building once their investigation is complete.

With files from CTV Atlantic's Dan MacIntosh