A London Underground line has reopened this morning after grinding to a halt when a cement leak damaged a signal control room.
The Victoria Line was closed between Warren Street in the centre of the capital and Brixton in the south after the leak from an area where contractors were working on a long-term upgrade of Victoria Station yesterday.
It left tens of thousand of rush hour commuters searching for an alternative way to get home.
A spokesman for Transport for London said the problem has been resolved and the Victoria Line is operating a good service.
Nigel Holness, London Underground's operations director, said contractors had been working on the new station in an area next to the Victoria line signal control room.
"These works involved the use of water and cement which leaked into the room, damaging equipment," he said.
Pictures were posted on the UsVsth3m website purporting to show a layer of cement in the affected room.
A spokesman for the RMT union said yesterday: " We understand that a foot of concrete burst into the control room, having been poured into an escalator void.
"We await further information but what we do know is that LU technicians are on site now, working flat out to clear up the mess and get services back on line, proving once again that it's directly-employed public sector staff who are needed to deal with this kind of emergency, making a nonsense of Boris Johnson's Tube staff cuts plans."
Peter McNaught, operations director for the Bakerloo, Central and Victoria lines, said: "Our engineers have worked tirelessly through the night and have successfully repaired the damaged signalling equipment. A good service is now operating across the Victoria line.
"We again apologise to our customers who were affected by yesterday's disruption."