An explosion in a section of pavement in a Soho street is thought to have been caused by a gas or electricity fault, the Met Police said.
No-one was injured when paving slabs shattered in Archer Street at about 17:30 GMT.
Opera singer Burak Gulsen described his "great shock" when the explosion happened in front of him.
"First I thought it was an attack. Everyone was screaming and I saw the pavement flying," he said.
The Met said it is not being treated as a terror-related incident.
Mr Gulsen, 39, from Dalston, north London, said he was about 5m (16ft) away from the flying pavement slabs on the opposite side of the street.
"After it happened a police officer came along and told people to move away. It was a great shock," he said.
"After that everything was normal again. People were eating, laughing, talking."