Trains cancelled due to 'hole above sewer' in Forest Hill
A 13ft-deep hole causing widespread disruption to trains in south London has been found to have opened above an active sewer.
Network Rail and Thames Water engineers are at the scene after the hole appeared in Forest Hill on Monday.
The disruption is expected to last until Wednesday, with Southern, Thameslink and London Overground services affected.
Thames Water said a sewer under the track had collapsed.
It said the repair work was "extremely complex" and that engineers had located the problem section of the sewer and were working to seal it.
Dry concrete has been put into the hole, forming a base to pour wet concrete on top. Once it has set, about 50 tonnes of ballast will be inserted, with the aim of opening the railway on Wednesday.
Network Rail has closed all four lines between East Croydon and London Bridge, meaning Southern services to London Bridge are either cancelled or diverted.
London Overground services are not running between West Croydon/Crystal Palace and New Cross Gate.
Carl Leadbetter, Thames Water's regional network manager, said: "Our teams continue to work as fast as possible on this critical job.
"While we need to work quickly to reopen the train lines, we also need to consider local residents, who will potentially suffer from sewer flooding if the pipe is not properly enclosed.
"This is an extremely complex job as the pipe is in a difficult location in the tracks and six metres below the ground."
Network Rail apologised for the delays and said it was working "as hard as possible" to get the problem fixed by Wednesday morning's rush hour.
Spokesman Chris Denham said the hole "couldn't be in a worse place".
"This is a massive piece of railway," he told BBC Radio London. "It's the equivalent of shutting the A2 out of London in the morning. It's absolutely huge."
Some passengers expressed their frustration on social media, mentioning how the problem occurred on the hottest day of the year so far.
Elsewhere in London, high temperatures have been disrupting trains between the city and the West, with speeds being cut over fears of rails buckling.
Trains coming out of Paddington, Euston and Liverpool Street all saw severe disruption.
And Southern services heading to Brighton from Victoria were heavily disrupted following a track failure in the Gatwick area.
It comes as commuters have experienced months of cancellations and delays on Southern trains due to an RMT dispute.
New rail minister Paul Maynard will appear before the Commons Transport Select Committee on Wednesday to give evidence on the Department for Transport's role in the issue.