A bizarre incident involving quick drying concrete appears to have shut parts of the Victoria Line.
There are currently severe delays, and no trains running between Warren Street and Brixton, due to what Transport for London (TfL) described as "damage caused by flooding".
However the UsVsTh3m website has posted a series of pictures purporting to show fast-setting concrete in the signalling equipment room and submerging rows of relay equipment. It says a civil engineering team is trying to get it out "ASAP".
TfL posted the following statement: "No service between Warren Street and Brixton while we fix damage caused by Flooding at Victoria. SEVERE DELAYS on the rest of the line. Tickets valid on South Eastern Trains, South West Trains, Greater Anglia, First Capital Connect (Great Northern), London Overground and London Buses via reasonable routes."
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Update: London Underground's operations director, Nigel Holness, said: "This afternoon our contractors were 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. This has meant there are no signals working on the southern section of the line.
"Our engineers are working hard to resolve the situation as soon as possible to get services back up and running, but the line is expected to be affected for the remainder of the day while repairs are carried out."
Transport for London apologised for the delays, and advised that a replacement bus service is in operation.
A spokesman said tickets are also being accepted on South Eastern Trains, South West Trains, Greater Anglia, London Overground and London Buses via reasonable routes.