The crash was west of downtown at 3:50 p.m., at the beginning of rush hour.
The investigators worked all night to identify with certainty the three victims and to make contact with their families and loved ones.
"It is with deep sadness that I report there were three confirmed casualties, two of which were on the bus and one that was on the platform", Ottawa Mayor Jim Watson told reporters at a news conference late on Friday.
While police initially took the female driver of the bus into custody, they said Saturday she had been released without charges.
OC Transpo has issued notices saying detours are in effect for the Dominion and Westboro transit stations.
Two of the dead were riding the bus; one was on the platform at Westboro station, a major stop on the city's busway, he said.
It is believed that some of those injuries in the crash were critical.
Emergency crews were called to Westboro station in Ottawa following a collision involving a double-decker OC Transpo bus.
Those who have pictures or video of the crash are being asked to get in touch with police, while passengers on the bus missing property are also asked to reach out. There were no patients taken to the Children's Hospital of Eastern Ontario, indicating there were likely no children among the injured. He said he didn't yet have precise numbers.
An investigation was opened to determine the cause of the crash, police said, adding that the bus driver was detained "and will be interviewed". Police said this morning that no information regarding the identities of the three victims will be made public at this time.
Bordeleau made it clear while police expect to release the scene Saturday, work collecting evidence, analyzing photos, videos and data, along with interviewing the almost 90 people on the bus is going to be a "slow, painstaking process".
"The bus started swerving, I guess it hit the curb or hit something".
"I was sitting in the exact same seat; it could have easily been me", she said.
Canadian Prime Minister Justin Trudeau sent his condolences to the bereaved and thanked emergency workers who responded to the scene.
"There was definitely people pinned and there was a bit of blood on the floor", Gill said.
- Hacienda patient may not have shown signs of pregnancy, expert says
- Junket tourism
- Tulsi Gabbard: Democrat says she will run for president in 2020
- Longer US government shutdown will hit economy: Federal Reserve Chief Jerome Powell
- ‘Bird Box Challenge’ leads to crash, possible charges for Utah teenager
- Bernie Sanders faces questions about political future
- US Bolsters Forces in Region as Syria Withdrawal Begins
- Toyota recalls 1.7 million vehicles in North America to fix airbags
- Transfer: Sarri speaks on Chelsea selling Willian
- USA air travel concerns surface as gov't shutdown drags on