The tragic incident, which took place on Monday, saw the crane fall to the ground where people were on the ground nearby.
Police have yet to confirm if those who had died were members of the crew or the public.
Those nearby have been evacuated as the structure has been deemed unsafe.
The development company says there was a “catastrophic failure” on Monday morning when the crane fell into an adjacent building and a home.
The crash, which took place around 10.45am PT (5.45pm GMT), occurred at the downtown Brooklyn building on Bernard Street in British Columbia, Canada.
So far, police have said there have been “multiple confirmed fatalities” but have not included how many people have died.
Three patients were also taken to hospital with “varying injuries”.
Inspector Adam MacIntosh also told the media that at least one person is missing – and confirmed that they were not part of the crew.
“It looked like the crane was moving but then I realized that it wasn’t moving in a fashion where it was operating, it was coming down,” witness Krista Roessing told CBC.
She then described how she called 911 as people rushed from all directions to help.
She added that construction workers asked people to back away and emergency services raced to the scene within minutes.
“It’s shocking,” she said. “It’s pretty hard to process.”
Anna Jacyszyn, who works nearby, said she saw a “huge pile of dust” after the cran fell.
“I was literally just praying and crying, because the emotions you get when you know that someone could be hurt is pretty drastic,” she said.
The area has been cordoned off for the investigation, with the British Columbia and WorkSafeBC conducting their own reviews into the incident.
Several workers were near the crane when it collapsed, with Insp MacIntosh adding “not all persons have been identified.”
He added that “the area remains unstable and unsafe.”
A four-block perimeter was evacuated with residents and drivers urged to stay away.
Power was disrupted to downtown and traffic is being rerouted away from the crash.
A structural engineer is studying how to make the area safe again.