Wayne Romaine, an investigator with the Ontario Fire Marshal's office, said a gas leak caused the massive explosion Monday afternoon, but it will be a while before the cause of the leak can be determined.
Romaine said that it would have taken "very little" to ignite the blast in this type of "gaseous environment."
A spark as little as that from the static electricity created from walking across a carpet could have caused the blast, or the electricity coming from a refrigerator or light switch, Romaine told a Tuesday afternoon news conference.
Romaine said investigators are using similar techniques to those used to figure out what happened in the Sunrise Propane plant explosion that killed one worker.
He said they have interviewed most of the residents nearby and nothing suspicious has been found, but said he couldn't rule that out just yet.
A fourth cadaver dog began sniffing the site Tuesday afternoon for bodies, Romaine said, although no one has been reported missing.
A neighbour suffered minor hand injuries in the blast, but no other injuries have been reported.
Romaine said investigators are still trying to figure out how the gas leak occurred.
"We're looking for migrant gases — is it possible that we have migrant gases that have come through the soil and into the basement," he said.
"We're looking for any type of indication as to the type of fuel that might be involved."
Police have identified a man who was pulled from the wreckage Monday as Paul Zigomanis. Romaine said he was found at the back of the house and pronounced dead at the scene.
Photographs of the scene show nothing but rubble left from the two-storey house. Debris was scattered over hundreds of metres, some of it hanging from trees and on neighbouring houses.
Romaine says there is little fire damage, which suggests the fuel was consumed during the explosion.
Investigators are expected to be at the site until Friday.