This is reported by The Daily Telegraph.

As established by law enforcement agencies, smoke at the metro station occurred after loud claps.

"The cause of thick smoke is associated with a malfunction of the train," - noted in the London Underground.

As a result, the Holborn metro station was closed due to the need to respond to fire alarm signals.

Now the law enforcement agencies are investigating all the details of what happened.

Recall, as previously reported, "URA-Inform," a few days ago in London, urgently evacuated people from the metro station Oxford Circus.