Commuters are facing travel chaos on some of the country's busiest routes after a lineside fire forced the closure of nine platforms at London Waterloo station.
South Western Railway passengers were urged to check their journeys and use alternative routes where possible after "significant damage" was caused to a number of cables on Wednesday.
Network Rail said its engineers will be working through the night to fix the damage but that the disruption might continue on Thursday morning.
Platforms 16 to 24 were fully closed on Wednesday at Waterloo after the fire.
A spokesman for Network Rail and South Western Railway said: "We are very sorry for the disruption South Western Railway passengers are experiencing.
"A lineside fire this morning caused significant damage to some of the rail infrastructure in the Waterloo area, fully closing platforms 16-24.
"Trains will be delayed or cancelled until the end of service today and disruption is likely to impact services tomorrow morning.
"Passengers are strongly advised to check their journeys before travelling at www.southwesternrailway.com for ticket acceptance and service details."
Trains between London Waterloo, Hounslow, Richmond, Strawberry Hill and Kingston were cancelled, while services between Waterloo and Windsor & Eton Riverside were diverted via Kingston.
Passengers were warned that services on other routes may also be subject to short-notice cancellations or delays.
Commuters facing travel chaos took to Twitter about the disruption, with many calling it "chaos" at Waterloo.
One person wrote on Twitter: "Anyone travelling west from Waterloo it is chaos. Been sent to Paddington but it is busy even at 3.15pm."
Another said: "Fed up of every time I am on SW train I get delayed. 2 hours on a train from Ascot to London and didn’t even make it to Waterloo."
Rail passengers also faced major disruption at Waterloo on Tuesday night, with trains being cancelled by up to an hour.
Services came to a halt after a person was struck by a train between Surbiton and Basingstoke.
The severe disruption worsened due to a separate passenger incident at Brookwood, SWR said.
