A woman is dead and a man has been airlifted to hospital after a house explosion in Kitchener, Ont.

Emergency crews were called to a home on Sprucedale Crescent, between Claycroft Crescent and Blackwell Drive in the city's south end, just after 8 a.m. ET on Wednesday.

The deceased woman and injured man have not yet been identified. Emergency officials said they were found in the backyard area of the home after the explosion. The man remains in critical condition at Hamilton General Hospital.

Police said both people appear to have "come from the residence," but it wasn't known if they were visiting the home.

"To our knowledge, at this point, everyone that we're aware of is accounted for. But we can't confirm that there is not anybody else in the dwelling, because we haven't been able to do that investigation at this point," said Deputy Chief Kevin Chalk, of the Waterloo Regional Police Service.

"We haven't been able to get to the scene for obvious reasons. It's still unsafe to do so and coroner has yet to arrive to the scene to examine the deceased person."

The house was levelled by the blast. The frantic moments just after the explosion were captured on camera and posted to Facebook. (Note: This video contains strong language.)

A witness captures the frantic moments after a south Kitchener home explodes 1:12

"We are currently actively fighting fires in three homes related to the explosion," Kitchener fire Chief Jon Rehill said shortly after 11 a.m. "This is a significant event that called all of our all available resources."

Rehill said 16 homes were evacuated and it will be at least three days before people can return to those houses. The two neighbouring homes were most significantly damaged, he said, and those residents will be out of their homes longer.

There is no damage estimate yet, Rehill said. "We're into the millions, there's no question."

Neighbour heard 'big boom'

Rehill said there was "significant damage" to the two houses on either side of the home that was destroyed, as well as one to the rear.

"When you have a house explosion like this, there could be many reasons for it," said Chalk. "Some of it could be criminal, some of it would not be. All options are open at this point, until we have a chance to use the residence and do that examination and that."

The house was not known to police, he said.

Sharee Bailie, who lives on the street where the explosion occurred, said flames and debris hit her home.

"All of a sudden, I just heard this big boom and everything was shaking and the lights went off. So I ran upstairs and I noticed that everything was off the walls and there was glass around," she said. "People were yelling, 'Get out of your house! Get out of your house!'"

Bailie said she saw that the house next door had collapsed and a fire had started.

"I imagine our curtains caught on fire, and the first level is supposedly not in good shape," she said.

Police said everyone seemed to be accounted for following the explosion at the home on Sprucedale Crescent. (Waterloo Regional Police Service/Twitter )

Other people living nearby told CBC News they felt the ground shake and they came out of their homes to see vehicles covered in debris, as well as home insulation scattered on the street.

There is currently no threat to neighbouring areas, Rehill said, but it was too soon to say when people might be able to safely return to their homes.

Police said gas and power nearby would be shut off for a "lengthy amount of time," and Kitchener Utilities was on standby to assist with any other shutoffs as needed. Water service was expected to be returned to the homes by Wednesday evening.

Officials are asking the public to avoid the area.