A garage explosion that killed two people and injured a third on Monday was caused when gasoline vapour was ignited by the open flame on a propane-fuelled heater. 

The explosion has been ruled accidental. Fire investigators say the vapour came from gas that spilled from a tank after it was removed from a vehicle. 

"It's the vapours that ignite," said Wayne Pawlowski, chief of investigations for Edmonton Fire Rescue. "Gasoline vapours, they say, are ten times more explosive than dynamite."

The bodies of a man and a woman were pulled out of the charred remains of the garage, while a man remains in hospital with burns.

Fire Marshal Tom Karpa said that the gas tank appeared to be quite close to the heater. 

"It would have happened extremely quickly," he said. 

At least five vehicles were parked in or near the garage when it exploded Monday at 6:38 p.m.

The man who lived at that Mill Woods home was always working on vehicles, said King Wong, who lives next door.

"He liked to deal with the cars, collect cars" he said.

Wong said the man works, but when he's at home, he's always in his garage. 

It appears three people were inside the detached garage on Lee Ridge Road when it exploded.

Neighbour Florence Magnan said she feared the wind would whip up the flames and cause the fire to spread.

"I was in my bathroom and all of a sudden I hear those sirens and I looked out. It was smoke at first and then the flame. I was so emotional, you have no idea, because(of) the wind."

Damages have been estimated at $85,000. 

Edmonton Police won't be releasing the names of the victims until their family members are notified.