The explosion in Pimlico Road in central London shook nearby buildings and left a gaping crater at the side of the road.
The Health and Safety Executive (HSE) said it was looking into the explosion which is believed to have been caused by a fault on the underground electricity network yesterday morning.
Cables at that spot, on Pimlico Road in central London, carry up to 11,000 volts.
Nearly 2,000 people in the area saw their power interrupted following the explosion.
