LONDON - A fire has broken out Friday (Aug 11) on board a train at London's Underground, and the Oxford Circus Tube station in the centre of the British capital's main shopping district has been shut down, reports said.

British police said the incident was not being treated as suspicious.

"We continue to work with @LondonFire at Oxford Circus. Station remains closed. Cause of fire not currently being treated as suspicious," British Transport Police said in a tweet.

London Fire Brigade posted a picture on Twitter which showed smoke billowing out of the open doors of a train.

"We have been called. We are investigating reports of a fire," a spokeswoman for London Fire Brigade said according to Reuters. "We are investigating and we are at the scene."

The station was closed while emergency services responded to the report, the city's transport authority said.

Passengers posted photos of what appears to be smoke pouring out of a Bakerloo Line train on social media as thousands of commuters were evacuated, reported The Independent.

One described fleeing the station as "f***ing terrifying", while others described smoke and the smell of burning plastic.

This story is developing.