Investigators are ready to rule out the possibility of foul play in a Winnipeg house fire in Winnipeg that claimed the lives of two senior firefighters, the Manitoba fire commissioner said on Monday.

"There's no indication at all to us that there's anything suspicious or whatever that it was intentional," said Doug Popowich.

Beyond that, Popowich said officials are still searching for clues that could tell what started the fire Sunday evening at the house of Appeals Court Justice Richard Chartier in St. Boniface. He said signs so far lead to the garage.

"What the first-in firefighter crews told our investigators [is] it all leads to the fire starting somewhere in the garage, so that's where we're going to concentrate our efforts first," he said, adding that investigators will begin their efforts by looking at entrances to the house.

"So now we're going to start to take the building apart, we're going to tear down the front, and then we're going to bring a steamer in, and start to thaw things out, so that we can get to the actual seat [of the fire]. We believe that it started somewhere in the garage area, but we need to confirm that so that's what we're going to start to work on."

Popowich said that so far, officials have determined the fatal flashover that killed Capt. Thomas Nichols, 57, and Capt. Harold Lessard, 55, happened minutes after firefighters arrived on the second floor of the house.

A flashover is what happens when gases ignite and create a flash of flame across an entire room.

Two other firefighters who were injured in the same flashover remained in hospital at Winnipeg's Health Sciences Centre Tuesday morning.

Senior firefighter Edward Wiebe, 51, remained in critical condition, while 33-year-old Lionel Crowther was in stable condition with burns to parts of his body. Two other firefighters were treated for minor injuries and released Sunday night.

Meanwhile, the funerals for Lessard and Nichols have yet to be scheduled. Jim Lee, president of the Canadian office of the International Association of Firefighters, said those funerals will draw people from across North America.

"We will put the call out across North America, and we expect firefighters from all over North America to be in attendance," he said Monday.

"It would be thousands, I am sure.… There's going to be a huge contingency of firefighters and uniformed services. The police always come out, too."

Ted Kuryluk, a 32-year firefighter who volunteers at the Fire Fighters Museum of Winnipeg, said Sunday's fire adds a new entry to the city's firefighting history.

"This is definitely tragic. We've never had anything this serious in recent years," said Kuryluk, who knew Nichols and Lessard. They were added Monday to the museum's Last Alarm list of firefighters who have died in the line of service.

Over the years, firefighters have been crushed by falling debris and succumbed to frostbite. In recent years, members have died of cancer and heart attacks. The last person to be added to the list before Sunday was Bruce Kitching, 48, who died in 2005 of a heart attack.

Winnipeg recorded its first firefighter death in 1896, when Charles Dawson died. The most recent firefighter to die on the job before Sunday was Lawrence Quinn, 40, who fell off a pump truck en route to a fire in 1990.

Kuryluk said the single biggest loss of life was in 1926, when part of a wall at the Winnipeg Theatre collapsed, killing four firefighters.

"We will not forget them," Kuryluk said of Lessard and Nichols. "We will not forget these two gentlemen who passed and the third who is the hospital right now fighting for his life.

"They will be remembered forever."