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.

Crews can now safely inspect critical equipment at our Finch Transmission Station. @TorontoHydro remains affected by an outage caused by the fire. — Hydro One (@HydroOne) July 28, 2018

Steeles/401/Kipling/Dufferin outage: we’ve restored power to as many customers as possible with approx.7,000 remaining out. @HydroOne is assessing damage at the transformer station and once we can get access, we should be able to restore all customers. — Toronto Hydro (@TorontoHydro) July 28, 2018

Steeles/401/Kipling/Dufferin outage: there is no change in the outage affecting 7,000 customers. We’re still waiting to access the scene at the transformer station. It’s difficult to estimate how long power will be out, but it’s possible this will be prolonged. — Toronto Hydro (@TorontoHydro) July 28, 2018