The Office of the Fire Marshal is investigating the cause of a fire that claimed the lives of 16 horses at Sunnybrook Stables early this morning.

Crews were called to the facility, located near Leslie Street and Eglinton Avenue, shortly after 3 a.m.

Toronto Fire Acting Platoon Chief Glenn Sherwood said the fire was first reported by residents of an apartment building on Leslie Street.

He said it was initially believed to be a grass fire but when police and firefighters arrived in the area, they discovered that the main barn at Sunnybrook Stables was engulfed in flames.

The flames had already started to migrate to a second barn but Sherwood said crews were able to quickly stop the spread of the fire.

At the height of the blaze, 16 trucks and upwards of 50 firefighters were on scene.

Crews removed 13 horses from the second barn, which sustained minimal damage, and transported the animals to the Toronto Police Service’s stables at Exhibition Place.

In an update on Monday afternoon, police said it appears 16 horses died in the fire.

Sherwood said three fire trucks were dedicated to assisting the police service in bringing the surviving horses to safety.

He said it was fortunate that they were able to save some of the animals.

“Even if it wasn’t fire, the smoke is just a deadly toxin as well so they could have perished just from the smoke,” Sherwood added.

Initially police closed Sunnybrook Park over concerns that some of the horses may have escaped and could be running loose.

“I have been told that they (horses) can become aggressive and be quite upset, understandably, in regards to what’s happened,” Sgt. Sean Cosgrove told reporters Monday morning.

"The determination was to close the park today and limit pedestrians as much as possible because it is a safety issue. We don’t want anyone getting injured.”

The Toronto Police Service’s Mounted Unit was also brought in to help search for any horses that may have escaped.

“We were working with the possibility that we had unaccounted for horses and the Mounted Unit was brought up here for their expertise and their knowledge to help make a safe situation for pedestrians,” Cosgrove said.

By Monday afternoon, Cosgrove confirmed that all horses are believed to have been accounted for and the park has now reopened.

Fire investigators have not been able to get into the main barn to begin probing the cause, origin, and circumstances surrounding the fire.

“The structure is too unsafe to make entry,” Sherwood said, adding that they may need to bring in heavy equipment to remove debris before anyone can get inside.

The Office of the Fire Marshal arrived on scene late Monday morning and will be leading the investigation.

Cosgrove said they have not yet determined if the fire is suspicious in nature.

“When a fire hasn’t been determined, all of our options are on the table when we are investigating,” he said.

“If anybody was in the park in the early morning hours, any part of the park actually, and they saw something that they deemed to be suspicious or that they would like to report to the police, I would really urge you to please contact us. No information is too small for us to consider.”

While updating reporters on the blaze, Toronto Fire Chief Matthew Pegg said sources have told them that there were reports of fireworks in the area on Sunday night.

“That information has of course been passed along to both Toronto police and to our investigators and the Ontario Fire Marshal and they will take that into full consideration as they continue their scene examination,” he said. “Whether that played a role in this fire – it’s far too early to tell but I’m confident that they will investigate these reports of fireworks.”

In a statement posted on social media Monday, Sue Iwan, the managing director of The Riding Academy at The Horse Palace, thanked firefighters and the police service's mounted unit for their efforts following the fire.

"On behalf of all of us at The Riding Academy and at Sunnybrook Stables, I want to thank everyone who took the time to reach out, come down, send condolences, and for the many thoughtful offers of assistance," the statement read.

"Our Sunnybrook and Horse Palace herds are cherished members of our family, and it is with incredible sadness that we mourn the loss of Mr. T, Beau, Sutherland, Sandy, Sampson, Axel, Sugar, Blossom, Poomba, Hercules, Apollo, Phoenix, Marty, Misty, Tess, and Gifford. These horses were wonderful teachers and friends, the best of the best. We loved them dearly, and we are beyond devastated. They are forever in our hearts."