Sleepy commuters had to wait to get on a tube this morning as a crew from Wimbledon fire station investigated the "smell of smoke" down at underground level.
The crew was called at 5.30am, but had to wait for the first tube to run before they could properly investigate and cause as little disruption as possible.
A spokesman for the station said: "There was a smell of smoke at Tooting. We investigated it.
"I think they had been doing some welding overnight and there was still some residual smoke."
The crew got on a slow train running between South Wimbledon and Tooting Broadway. The doors remained open and a thermal imaging camera used to detect if there was any fire.
None was found and firefighters left the underground at about 6.30am.
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