A central Toronto house is in ruins after it was firebombed Sunday night, the third time it has been targeted this month.

The caller who reported the fire to 911 told emergency officials the fire ignited when at least one Molotov cocktail was tossed at the back of the home, a Toronto Fire Services spokesman said.

Police wouldn't reveal the cause but said the fire is being investigated as an arson.

The same house, located at 489 Winona Dr., was shot up and firebombed in separate attacks just weeks ago.

Sunday's massive five-alarm blaze broke out about 9:50 p.m. and drew more than 100 firefighters.

Flames gutted the three-storey house, near Oakwood and Eglinton Avenues, and damaged neighbouring homes.

Nearby residents were evacuated as a precaution as firefighters tried to stop the blaze from spreading even further.

Toronto Police Staff Sgt. Courtney Chambers said the occupants – a man, woman and two children – were home at the time and were safely evacuated by police officers.

The homeowners have been identified as Bojidar Zahariev and Patricia Valdebenito. They have a six-month-old daughter and a four-year-old son.

Police also said that they have a person of interest already in custody on an unrelated matter. Officers would not elaborate, but it's believed the man is charged with uttering threats.

An adult in the home suffered mild smoke inhalation, Toronto Fire Capt. David Eckerman told ctvtoronto.ca.

Chambers said the first two officers who arrived and led the evacuation were treated on scene for minor smoke inhalation, while a third officer suffered a slight back injury when she slipped on ice that formed as firefighters sprayed water on the flames.

All three continued their shifts, he said.

Firefighters used at least two ladder trucks to douse the flames, which extended several metres into the air. A large plume of smoke billowed into the night sky.

"I could just smell something funny and then when I looked out my window I saw smoke," a woman told CTV as the house burned. "That's an incredible fire."

A second witness said all three storeys were engulfed in flames.

The blaze was finally brought under control and put out early Monday.

Police told reporters one person is in custody "on an unrelated matter" after allegedly threatening the family's lives earlier this month. Police released no other details.

Chambers said police are investigating whether Sunday's fire is linked to the earlier attacks.

Several gunshots were fired at the home and a car in the driveway Dec. 3. No one was injured.

A few days later, on Dec. 6, Molotov cocktails were tossed at the residence. At least one of the homemade firebombs ignited but the flames were stomped out by police officers who responded a few minutes later. No injuries were reported.

The home was recently put on the market for $729,000, but it did not sell.

With a report from CTV Toronto's Austin Delaney