Toronto police are investigating a single-vehicle crash in North York this morning that left one woman dead and a man seriously injured.

Police were called to the area of Cummer Avenue and Craigmont Drive, near Leslie Street, at around 1:45 a.m. after receiving a report about a serious collision.

Investigators say it appears a vehicle was travelling east on Cummer Avenue when the driver failed to negotiate a curve and collided with the edge of a bridge.

The 25-year-old female driver of the car was pronounced dead at the scene, paramedics confirmed to CP24 Thursday. A 27-year-old male passenger was rushed to a trauma centre with life-threatening injuries but police say the man is now in stable condition and is expected to survive.

“How the passenger survived is beyond me,” Const. Clint Stibbe told CP24 at the scene Thursday. “The damage on this car is tremendous. That’s the only way I can describe it.”

Stibbe added that the passenger was wearing a seat belt but the driver was not.

Investigators are still trying to determine what caused the crash but Stibbe said speed is "definitely a factor."

“What we are looking at is what happened prior to this collision. The other question that we have to ask is how long was this car here? This isn’t a very heavily travelled road during the night and as I understand it, this vehicle may have been here some time prior to somebody actually finding it,” Stibbe said.

"We are asking anybody who was driving through the area last night to let us know what time they came through just so we can kind of narrow down when this collision actually did occur." 

He added that a full examination will be conducted on both the deceased driver and the vehicle.

“There doesn’t appear to be any braking and we have to see if there was any sort of mechanical failure of the vehicle braking system or something else that may have happened just prior to the collision,” Stibbe said.

Police have not yet released the name of the victim killed in the crash.

"In the end, what we have is a family unfortunately that has been devastated at the loss of their daughter," Stibbe said.