The Ontario Ministry of Labour is probing the circumstances of how a crane toppled down in northwest Toronto on Monday afternoon, bringing down hydro poles and associated power lines that came to rest on a TTC bus.

Toronto police were called to the scene near Kipling Avenue and Rexdale Boulevard around 1:21 p.m. on Monday.

The crane collapsed at around 1:20 p.m. ET. (@tammyralph/Twitter)

The mobile crane downed several hydro poles and wires, which came down on top of a TTC bus that was heading northbound on Kipling Avenue. Emergency workers and police were at the scene soon after being alerted of the collapse.

About 30 passengers on board initially had to stay in the bus as a precautionary measure because the wires were possibly live.

But at around 2:20 p.m., Toronto police Const. Ryan Willmer tweeted that passengers were being escorted off the bus and "seem to be okay."

The crane operator was also trapped, but has now been taken to hospital.

The extent of his injuries are not known, said Supt. Ron Taverner, but they are not believed to be life-threatening.

No injuries have been reported. Investigators from the labour ministry arrived on the scene on Monday afternoon.

Taverner praised the TTC bus driver for keeping the passengers calm, given the circumstances.

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"She really is a hero," he said.

That stretch of Kipling Avenue could be closed for days, given the need to safely move the crane and ensure the wires are safe.

Even though wires are down, there is a concern they could become live again, said Taverner.

The power has been cut in the area, and approximately 400 Toronto Hydro customers are without power. Toronto Hydro doesn't know when power will be restored to those customers.