Fire crews were called to the Bloor-Yonge subway station at around 10 a.m. on Tuesday morning after a fire broke out on the southbound platform, officials say.
Toronto Fire Services told Global News crews responded and found smoke in the tunnel with visible flames.
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Officials said the power was cut at the station while crews extinguished the fire.
Toronto fire said the blaze was extinguished and that smoke from the tunnel had been cleared.
Officials said no injuries were reported.
The fire started in an electrical control box, Toronto fire said.
The Toronto Transit Commission (TTC) said trains would not be stopping at the station due to a fire investigation.