Thames Water is facing a multi-million pound bill over a burst main which poured 50,000 litres of water into a railway tunnel on Friday.

The leak to a 16 inch pipe, between St Pancras and Farringdon, has hit tens of thousands of passengers on Govia Thameslink services around south London since then.

From Friday: Travel chaos after burst water main in rail tunnel

From Monday: VIDEO: Train struggles through the flood water which ruined commutes across south London this weekend

More than 1,000 trains had been cancelled and 133 hours of combined delays in lines which see up to 200,000 journeys a day, Govia said today.

But the rail firm said that Thames Water had found four more leaks and water was still spilling into the tunnel.

Phil Verster, route managing director of Network Rail, said: "We expect Thames water to reimburse passengers, train operators and Network Rail for the significant consequences of these water leaks."

And Stuart Cheshire, Govia's passenger services director for Thameslink, said: "Passengers have been very patient but, like us, that patience has been utterly exhausted. These recurring leaks have to stop."

He said: "Tonight our passengers will have another very difficult journey home. We will have to thin out our services before cancelling them altogether between St Pancras and Farringdon.

"We are arranging for buses to run between the Great Northern route and Thameslink as well as for our tickets to be accepted by all other operators. Please accept our apologies and visit thameslinkrailway.com for the latest information."

Chris Featherstone, head of operational control at Thames Water, said: "We’re very sorry for the delays commuters have experienced since Friday.

"We know this is a critical job and we’ve got our best teams working as fast as possible to discover where this water is coming from.

"We’re investigating every possibility, including checking all our sewers and water pipes in the area, and we will leave no stone unturned to find out what is happening in that tunnel."

Online commenters suggested that Crossrail excavations might be responsible for the leaks. On January 24, tunneling machine Ada ended her two-and-a-half year journey from Paddington to Farringdon.

Ada is one of eight 1,000 tonne, 150 metre long underground 'factorys' tunnelling 100 metres a week to create a network under central London from Reading and Heathrow in the west to Shenfield and Abbey Wood in the east.

Asked today about the rumour a spokesman for Crossrail said: "Absolutely not."