Fire Chief Dan Pistilli said the fire began a little before 3 a.m. in the 400 block of Ridgeway Avenue.
"En route, it was quite obvious with the amount of smoke in the air that we had a substantial fire going," said Pistilli. "Crews arrived on scene, heavy smoke and flame had extended from the back of the house up into the roof area."
Resident Wendy Devine was sleeping upstairs when the fire started.
"I don't know why I woke up, and I saw outside and there was big yellow flames and smoke. That's when I started shouting, and just told everybody, 'There's fire!' So I just grabbed my daughter and told my husband to grab the baby," said Devine.
"I just started banging on everyone's rooms."
Pistilli said 11 or 12 people got out safely, and nobody was hurt.
"I'm just glad everyone's safe," said Devine, who added that she couldn't see, because she didn't have time to grab her glasses. She said her family left everything inside.
"Emergency Social Services will take care of the residents for the near future, then we'll have to take it from there," said Pistilli.
"I've seen places with worse damage than this that have been repaired, so we're hopeful the place can be repaired," he said. "But not any time soon."
Investigators will inspect the damaged house to determine the cause. Pistilli said it's too early to say how the fire started.