An explosion that killed a 58-year-old woman, critically injured a man and levelled a home in Kitchener, Ont., is suspicious, and the woman's death is a homicide, police say.

The explosion happened around 8 a.m. Wednesday morning on Sprucedale Crescent in the city's south end.

Edra Haan was found dead after the blast. Her husband, Udo Haan, was critically injured and airlifted to hospital in Hamilton, where he remained on Thursday.

On Thursday, Waterloo Regional Police Service said they have determined the explosion is suspicious.

"At this point, we are investigating the circumstances," said Insp. Mike Haffner.

Police are waiting for the male victim to be released from hospital, he said, "so that we can question that individual in relation to the circumstance of this explosion."

He added: "We're looking forward to speaking to that individual but, at this point, he's not a suspect."

Police have not confirmed that Udo Haan was the man injured in Wednesday's explosion, but his employer, Sun Life Financial, issued a statement Thursday, saying both he and Edra worked at the company's Waterloo office.

The company said it was deeply saddened to learn of Edra's death and Udo's injuries, and "our heartfelt condolences and thoughts go out to their families, friends and colleagues."

Firefighters spent much of Wednesday putting out hot spots in and around the collapsed home.

Heavy machinery was brought in Thursday afternoon to go through the remainder of the home. Deputy fire chief Rob Martin said officials hope the investigation will be completed by the weekend.

Waterloo Regional Police Service said members from the Ontario Office of the Fire Marshal were called in to investigate after a fatal explosion in Kitchener. (Waterloo Regional Police Service/Twitter)

'A curtain of insulation coming down'

Residents of 12 houses in the area around the explosion have been told they may be able to return home Thursday evening. Among them is Joan Thompson, who lives four houses down and had seen the Haans around the neighbourhood walking their dogs.

She said she remembered hearing a "crash, boom" on Wednesday morning.

"It had just started raining and the dark clouds were coming over, so we at first thought it was a lightning strike," she said. "We were looking out the front window and there was this rain of stuff in the sky coming down. It looked like leaves … but it was insulation; it was just a curtain of insulation coming down."

The families living on either side of the house that exploded will be out of their homes for a much longer period of time, officials said, although a timeline wasn't given.

Some other residents along the street were able to return home on Wednesday night.

There is no damage estimate yet.

The Red Cross and Victim Services have been brought in to help residents affected by the explosion.