The crash took place at 3:50 p.m., during Friday rush hour, at Westboro station in an urban neighbourhood.
A double-Decker bus has in Canada's capital, Ottawa, is a stop-bus shelter rammed, leaving at least three people have died.
The driver was taken to the police station for an interview and released Saturday without conditions, Ottawa Police Chief Charles Bordeleau said. Chief Bordeleau also added Saturday the public shouldn't draw any conclusions from the initial arrest of the driver.
He says the investigation will be lengthy as multiple agencies collaborate to piece together what happened.
During the emergency response, a dozen ambulances lined one side of the transit route, waiting to take injured people away.
Sgt. Cameron Graham from the collision investigation unit, the team overseeing the investigation, told reporters on Saturday they're exploring a number of aspects, including "human factors", the vehicle itself and weather conditions.
"I heard a bump and I saw the bus crashing into Westboro Station", the local student told CTV Ottawa, still visibly shaken from what he had seen.
She says their names will not be released at this time.
While the National Transportation Safety Board does remain on the scene of the crash, Bordeleau said they are not involved in the investigation but collecting data for a study being conducted on similar crashes.
It's the second fatal OC Transpo double-decker bus accident the city has witnessed in five years.
"The bus started swerving, I guess it hit the curb or hit something". "A lot of people screamed, the people in the front were trapped under their Seats".
The bus had a capacity of 90 people, both sitting and standing.
"There was definitely people pinned and there was a bit of blood on the floor", Gill said.
This wasn't the only crash on the road Friday.
I also want to applaud the heroic efforts of our first responders, our emergency room nurses and doctors, and everyone who answered the call today.