A gas serviceman suffered second-degree burns Wednesday in a massive explosion that destroyed a house in midtown Toronto and damaged two others.

Firefighters were called to the four-alarm blaze on Harper Avenue, near the St. Clair Avenue East and Yonge Street intersection, around 11 a.m. ET Wednesday.

A firefighter stands by a truck as the remains of a house burns in the background in Toronto on Wednesday.
(Aaron Harris/Canadian Press)

"The house is, for all intents and purposes, gone," said Don Marsden, acting district chief of Toronto Fire Services.

A neighbour dragged the Enbridge gas employee, who had been working in the basement of the house, to the curb, Marsden said.

When emergency crews arrived, the man was transported to hospital. He was conscious and breathing. No other injuries were immediately reported.

It wasn't clear whether any members of the family that lived in the house were home at the time, although neighbours said the two children would likely have been at school.

A house on one side of the razed house also caught fire, while another was scorched by the heat, but the damages have been described as repairable.

The fire continued to burn in the basement of the destroyed house until gas company employees were able to shut off a natural gas line.

Fire officials said the blast may have been caused by a natural gas leak.

About a dozen homes in the surrounding area were evacuated by police as a precaution.

Ontario's fire marshal was called to the scene and launched an investigation.