Toronto fire officials say they are treating a massive four-alarm fire that destroyed two restaurants in Toronto's upscale Yorkville area Christmas night as "suspicious."

Emergency crews were called to Spuntini Ristorante & Bar and Sotto Sotto Restaurant, just before 7:30 p.m. on Thursday.

Both are known for serving celebrity patrons, from Jennifer Garner to Brad Pitt.

At the peak of the fire, some 22 fire trucks and 90 firefighters battled the blaze. Fire officials say it caused more than $1 million in damage.

The co-owner of Spuntini said on Friday that he was “traumatized by this.”

An employee of Sotto Sotto called it sad.

“It’s not just a restaurant,” said the worker, “it’s our family.”

Marisa Rocca, owner of Sotto Sotto, issued a statement on Friday promising to rebuild.

"We owe it to our history, our team and our loyal patrons to rebuild and we will come back stronger than ever," Rocca said in the statement.

The Ontario Fire Marshall visited the scene Friday and was expected to spend much of Saturday there as well.

So far, fire officials believe the blaze began at 116 Avenue Road before spreading to the neighbouring building.

The fire is being treated as suspicious because the building had been unoccupied for a few days and because of the extent of the damage, according to Toronto Fire Services.

The two restaurants were closed at the time, and officials said the tenant who lived in the apartment above the restaurant was away visiting family.

Both restaurants have been landmarks in the Yorkville community for over two decades, popular with celebrities during the Toronto International Film Festival.

A section of Avenue Road that was closed after the fire was expected to stay shut on Saturday.

Fire fighters remained at the scene overnight Friday in case of a building collapse.

Smoke was 'billowing'

According to fire officials, the heat from the fire was so extreme that at times firefighters were forced to back away.

Flames were seen jetting out from the building, and heavy smoke was visible on the street.

"We looked over at the restaurant and we noticed a lot of smoke coming out," a witness told CTV News. "At first I thought it was someone doing laundry or something, but then we realized it was billowing. We called 911 right after that."

One firefighter sustained minor burns, but was treated on the scene and remained on duty.