Toronto Hydro says thousands of city residents are without power after a fire at a hydro station.

Police say they responded to calls of an explosion at the station in northwest Toronto just after midnight Saturday, and found the hydro vault had caught fire.

They say the power was shut down so the fire could be put out.

Toronto Hydro says it doesn't have an estimate for when power will be restored.

The utility says the outages affect about 7,000 customers in the Steeles and Dufferin area.