Streets were evacuated last night in Northampton after a two electricity substations caught fire.
Residents in the areas around Semilong Road were told to leave their homes after the fire started around 9.15pm last night.
Homes across NN1 and NN2 areas have also been left without power this morning, as Western Power Distribution works to recover supply.
Four fire crews from Northamptonshire Fire and Rescue were still fighting the flames long after midnight.
People who live in the flats directly behind the substations were told to leave their homes in case the fire spread or caused smoke damage.
Residents in other nearby areas were advised to keep doors and windows closed.
The cause of the fire is not yet known.
Western Power Distribution have apologised to all the residents going without power this morning, and said engineers were doing all they could to restore power for everyone by 9am.