Updated: Thu Oct. 29 2009 9:54:18 PM

ctvtoronto.ca

One man is suffering from life-threatening burns and three more people from lesser ones after an explosion rocked a home in northwest Toronto overnight.

"It keep going, exploding. Then the fire blew. It was a big bonfire," said neighbor Lucy Gaiardo late Wednesday evening.

Another neighbour said the fire lit the sky right up.

Six people who were inside the home managed to get out, but a 24-year-old man is in life-threatening condition in hospital. He is suffering from third-degree burns to 90 per cent of his body.

The victims were in the bungalow at 33 Amesbury Ave. in the Lawrence Avenue West and Keele Street area when the explosion happened around 10 p.m. Wednesday evening.

A 17-year-old boy was taken to a hospital in Hamilton to be treated in a special burns unit.

Two other men who were in the home suffered minor burns to their arms, hands, faces and necks.

A woman and a two-year-old child in the home walked away uninjured.

"There's not a single wall standing," Toronto Fire Capt Adrian Ratushniak told ctvtoronto.ca. "There's some remnants of exterior brick walls but for the most part it has been flattened."

Firefighters managed to douse the flames despite the fire being fed by a natural gas line.

As to the cause, "One of the homeowners was doing some maintenance to the furnace and there was an explosion," said Jim Gillespie of the Ontario Fire Marshall's Office.

Ratushniak said it is important for homeowners to properly maintain furnaces, fireplaces, boilers and fuel burning appliances to prevent fires, explosions, and potentially lethal carbon monoxide leaks.

"We want the public to make sure they are taking proper precautions to get their furnace maintained properly," Ratushniak said.

Gillespie said: "Unless you're qualified and know what you're doing, don't do it. It's obviously quite dangerous ... just leave it to the professionals."

People who live in six other homes on the block were temporarily evacuated, but their homes were not damaged and they were not injured.

With a report from CTV Toronto's Jim Junkin