A building housing a popular Greektown diner that was the site of a four-alarm fire on Tuesday morning is believed to be a total loss, according to officials.

The fire started in the basement of the Detroit Eatery, located near Chester and Danforth avenues, at around 6:40 a.m.

“Crews arrived. They located a fire in the basement. There was heavy smoke. They couldn’t actually get to the fire. At one point the building was compromised, the structural integrity. Crews had to withdraw,” Division Commander Greg Weeks told reporters at the scene on Tuesday morning. “It was hard to get to the seat of the fire to extinguish it.”

The fire was finally knocked down at around 10:30 a.m., about four hours after it started.

Speaking with CP24 on Tuesday afternoon, Deputy Chief Jim Jessop said that the floor in the building has completely caved in and that the structure is likely a total loss.

He said that while there is nothing to suggest that the fire was suspicious at this point, the cause remains unclear.

“There was a significant amount of water used to extinguish the fire,” Weeks said earlier in the day, noting that the extreme cold added to the challenges firefighters faced extinguishing the blaze.

“Cold is always an issue,” Weeks said. “We are constantly cycling crews through to keep them warm.”

No injuries were reported but the diner sustained significant damage.

Becker's Bridal and another adjacent business also sustained smoke and water damage, Weeks confirmed.

Danforth Avenue is currently closed between Jackman Avenue and Logan Avenue.

“We have to pump the water out and then our investigations team has to come in and do a full investigation,” Weeks said.

It is not yet clear if the Office of the Fire Marshal will be called in to investigate.

“If it is more than $1 million in damages they automatically come in,” Weeks said.

Speaking to CP24 on Tuesday morning, a patron of the diner called it a "sad day" for the Danforth.

“They had a lot of hockey paraphernalia that if it is burned, it can’t be replaced," he said. "This was a wonderful place, wonderful people and it is really a shame to find out this is on fire."

Meanwhile, another patron of the diner who represented the neighbourhood as its Member of Parliament from 1988 to 2004 recalled bringing multiple sitting Prime Ministers to the establishment.

“This wasn’t a business, this was a family home experience,” Dennis Mills said. “In 1987 when I started my campaign it started at the Detroit. I brought Prime Minister Chretien here, I brought Prime Minister Turner here, my wife brought Prime Minister Trudeau here.”

Customers who frequent the diner also took to Twitter to express their support for the owners and staff on Tuesday.

If you’ve visited me in Toronto, there’s a 100% chance I took you to @DetroitEatery. It’s impossible to categorize. The people - from all walks of life in parallel universes - are what makes Detroit so special. The Danforth will rally to support Chris in a mind-blowing way. pic.twitter.com/2qvPWHxf5W — John Sharkman (@JohnSharkman) January 22, 2019