An explosion and fire at an electric sub station let to a power cut in Hartlepool.
An estimated 22,000 homes were left without power at the time of the explosion, which also affected power supplies in the town.
Smoke was sent billowing into the air after Saltburn's electrical substation burst into flames around 7pm on Monday evening.
A spokesman for Cleveland Fire Brigade said: "Following a power surge, there was an explosion in an electrical box."
There are no injuries reported but residents in Redcar, Teeside and Hartlepool were all affected and people who live close to the substation were warned to stay away from the area.
Underground cables have been affected, according to Northern Powergrid, and local residents described hearing bangs and loud rumbling noises.