British firefighters said on Friday they were investigating reports of smoke at Oxford Circus underground station in the center of London's main shopping district.

"We have been called. We are investigating reports of a fire," a spokeswoman for London Fire Brigade said. "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. Police said they had been called to the station after reports of a fire alert, Reuters reported.

Passenger Tom Singer tweeted a photograph of smoke filling a carriage of a Bakerloo Line train at the station

Passengers say staff ordered everyone to leave around 9 a.m. (0800GMT) Friday.

There were no immediate reports of injuries, the Associated Press reported.