A York Regional Police officer recovering from smoke inhalation says he was just doing his job whe he ran into a burning house in Markham on Tuesday.

Emergency crews were called to Douglas Haig Drive near McCowan Road and Steeles Avenue just before 5 p.m. after a reported explosion sparked a massive fire that destroyed one residence and damaged to another.

Speaking with CTV News on Wednesday, Const. Kynan Walper said he ran into the adjacent home to make sure nobody was inside and was “taken by surprise” when he encountered heavy smoke and saw flames that were travelling up a living room wall.

“I was thinking this is a very bad place to be,” he said. “If anyone was going to answer me or if anyone was inside it had to be done very quickly because I didn’t know what caused (the explosion) but I thought maybe it could be a gas line and there could be more stuff that is going to explode next door.”

Walper said that when he arrived on scene he looked up in the air and saw the “largest cloud of smoke” he had ever seen.

The constable said he then encountered a “badly injured man” outside the house that had been gutted by fire but decided to move on when he realized that paramedics were there to take care of him.

That’s when he decided to enter nearby homes to make sure that they had been evacuated.

“If you believe that there is someone inside as a police officer and you can act on it, that is your job to do that,” he said. “It is a calculated risk.”

A total of six people were injured in the blaze, including Walper and three children.

Five of the six injured parties were, however, released from hospital by Tuesday night. The other victim remains in hospital in serious but non-life-threatening condition.

Speaking with CTV News at the scene of the fire on Wednesday, a supervisor with the Ontario Fire Marshal’s office said that his investigators won’t be able to fully begin their probe until they can be sure that what remains of the home is structurally sound to enter.

“We have to be aware of what the building is like and the stability of the building so we know that it is safe to get in there and start digging out piece by piece to confirm what went on,” Lonnie Schubert said. “Until we get in there and start picking it apart piece by piece we won’t know.”

Walper said that the initial explosion was followed by several smaller explosions, which made for a “chaotic” atmosphere with large crowds gathering on the street.

The cause of the reported explosions and ensuing fire remains unknown, however.

“We will keep our eyes wide open and look at where the explosion may have occurred from, what fuels may have caused it and what ignition sources there are,” Schubert said.

With a report from CTV Toronto's Austin Delaney