Flames erupted out of manholes on a main road in east London after an electrical fire underground.
At least two explosions rocked Mare Street in Hackney after a fault developed at a junction box.
Eyewitnesses reported two loud bangs outside Hackney Town Hall followed by flames erupting from the ground.
There have been no reports of injuries.
A safety cordon was put up and roads were closed off leaving people stranded as they tried to get into work.
The London Fire Brigade and police said they were called to reports of explosions on Mare Street at 9.33am.
A spokeswoman for LFB said: “Firefighters from London Fire Brigade have been called to reports of a fire and explosion under the pavement on Mare Street in Hackney.
“It is believed that an electrical intake box under the pavement caught fire. Mare Street is closed in both directions from Morning Lane to Paragon Road.
“Firefighters have set up a 25 meter safety cordon.
One fire engine and five firefighters and officers from Homerton fire station are at the scene. The electricity provider has been called.”