"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 its 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."
More top news
London mayor Sadiq Khan is "extremely worried" about knife crime as the Met Police revealed there were 9,000 stabbings in the capital.
Camden police have responded to reports of an unexploded World War Two bomb in Hampstead high Street.
AFC Wimbledon face Plymouth in the League Two play-off final at Wembley, with a place in League One at stake.