At least four Toronto office towers have been evacuated and members of the public are being asked to stay away from parts of the downtown core after a construction crane crashed into the side of a building.

Emergency crews were first called to Wellington and Simcoe Streets around 10 a.m. for reports of a collapsed crane.

Calling the situation an "industrial accident," Toronto Police said that a crane had hit a building and that the machine's operator had sustained minor injuries.

#Toronto Fire on scene on a crane collapse at Wellington & Simcoe. @TPFFA @Toronto_Fire @ChiefPeggTFS @HighRiseUnit @FirehouseTrain1 pic.twitter.com/bLw3NmIkpK

— Derek Craig (@DerekCraiggers) July 16, 2020

Toronto Fire Chief Matthew Pegg told reporters at the scene, however, that the crane's operator had managed to emerge unharmed.

"The operator is not injured. She made her way down with the assistance of one of her colleagues and was down upon our arrival," said Pegg, noting that there were no additional injuries to report.

It is not yet known what caused the crane collapse, but fire officials are now concerned about the possibility of it falling further.

@Toronto_Fire crews have secured the section of the crane that is on the building. We are now working on securing the remainder of the crane. Hoisting engineers on scene. Mobile crane is en route. No injuries reported.

— Matthew Pegg (@ChiefPeggTFS) July 16, 2020

"We just need to deal with the public safety hazard, given I am told the crane is just about 200 feet in the air," said Pegg.

"We need to secure that and make sure that it doesn't end up with a subsequent incident."

The buildings at 40 University Ave., 145 Wellington St. W., 144 Front St. W. and 146 Front St. W. have all been evacuated and fire officials have secured a "collapse perimeter" around the crane in case it moves.

A construction crane at Front/Simcoe #Toronto has partially collapsed and crashed into an office tower. Worksite has been evacuated; emergency crews on scene pic.twitter.com/gF7zafHfwG

— Tracy Tong (@TracyTongTV) July 16, 2020

Pegg estimates that it could take about 12 hours to secure the remainder of the crane, but that the operation could be complicated by incoming thunderstorms.

"Obviously we can't control or prevent the movement or failure of the crane at this point. We are taking every precaution we can to make sure that it is secured," said Pegg to reporters.

"We're having to keep an eye on the weather. Fortunately, it's okay right now, but we're paying particular attention to weather moving through. We have to be very vigilant about things like heavy rain, wind and the potential for lightning."