Four people, including two children, were sent to hospital early Tuesday morning after a fire broke out at a Toronto highrise.

Police said emergency crews were called to Ontario Street and St. James Avenue at 3:11 a.m. for reports of a blaze in an apartment unit.

Toronto fire Division Commander John Carson told reporters that crews faced heavy heat and flames but were able to knock down the fire quickly.

Two adults – a man and a woman – and two children ages 12 and 14 were sent to hospital. The woman and children were being observed, Carson said, and the man is being treated for second-degree burns, Carson said.

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He added there were batteries and e-bikes on the balcony of the unit, and there were a couple of batteries inside the unit.

“The batteries were compromised inside and then outside. It certainly would have contributed to the intense burn,” Carson said.

An investigation into the cause of the fire is ongoing.