A small white dog acted as a fire alarm, waking its owner to alert him to a fire consuming several row houses in Kensington Market early Monday morning.

The dog may have helped save the lives of several residents who were sleeping while four row houses were burning. The dog pawed awake its owner, who is hard of hearing, and who in turn woke neighbours and helped them escape.

The fire started on the deck of one of the homes on Oxford Street at about 1 a.m., Toronto Fire Captain Mike Strapko told CTV Toronto.

It quickly spread to nearby homes, and approximately 110 firefighters and 20 trucks were needed to knock the fire down.

"The smoke was so thick you actually couldn't see the units. You could see red fire but you couldn't see any of the building," one neighbour said.

Firefighters are still putting out hot spots, but the fire was mostly extinguished by 3:30 a.m., Strapko said from the scene. They're monitoring the hot spots from the outside, as there is concern that one of the walls may collapse due to structural damage.

The estimated damage to the homes, located at 10, 12, 14 and 16 Oxford St., is approximately $1 million, firefighters said.

No humans were killed, but officials said five cats that belonged to a retired couple died in the fire.

"The flames were up to the top of the window and the window exploded and I yelled to Sheila, 'Let's get out,'" Richard Porter told CTV Toronto.

He said the blaze destroyed nearly everything he owns, and he does not have insurance.

Toronto Fire Services have asked Telus to donate a phone to Porter and his partner. They will be staying at local motel for free for the next few days while they figure out long-term plans.

Possible arsonist in the area

Officials are looking for surveillance footage as they investigate the cause of the fire.

A Toronto Fire division commander told reporters at the scene that there have been recent suspicious fires nearby, including one last week in a garage on Augusta Avenue. The Fire Marshal will be looking to see if there's a "fire bug" in the area.

With a report from CTV Toronto's Janice Golding