UPDATE: 1PM Baker Street Tube station and surrounding shops and flats have been evacuated due to a gas leak.
Thousands of people had to be evacuated after the leak was detected at 9am.
The source of the leak has been traced to the basement of a shop opposite the busy central London station.
Twenty shops and a seven storey block of flats have been evacuated.
Traffic has been closed to Baker Street from Allsop Place to Marylebone Road.
Trains are running non-stop through the station and the Metropolitan Line has minor delays due to the closure.
Engineers are now digging down to access the damaged pipe.
It's expected the repair work will take most of the afternoon and the closures would have to remain in place.
A National Grid spokeswoman said: "It appears a third party contractor damaged a gas service pipe in a shop opposite the station.
"Engineers have traced the source and are now trying to stop the leak.
"The situation is under control and the evacuation is a precaution."
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