Rail users have been urged to avoid London Bridge or expect heavy delays after a pothole under a track caused travel chaos.
Emergency repair works at Forest Hill, the second such incident in a month, caused Thameslink, Southern and London Overground services in south-east London to be delayed or cancelled on Thursday morning.
Southern services are not stopping at number of stations, including: Norwood Junction, Anerley, Penge West, Sydenham, Forest Hill, Honor Oak Park, Brockley, and New Cross Gate.
Commuters were initially warned the disruption could last until 6pm, but have now been told it will last the rest of the day.
Robert Coulson, Network Rail acting director, said engineers would be continuing to fix the problem for the remainder of Thursday.
"I’m really sorry that passengers have had to put up with this disruption today and I know that people are upset and will want to know we are doing everything we can to return their railway to them", he said.
Passengers are advised to use either Victoria or Blackfriars tonight.
Southern tickets are being accepted on London Buses, London Underground, Southeastern and Tramlink between Beckenham Junction and Croydon.