Derailed train at London Paddington remains for rush-hour
A train which derailed at London Paddington will remain on the track to allow for "maximum capacity" during Friday afternoon's rush-hour, Network Rail has confirmed.
The train, which crashed into a pylon as it derailed, won't be moved until after 22:00 BST.
Platforms one to five are closed due to damage caused to signalling and overhead wires.
Great Western Railway warned passengers of "significant disruption".
The empty train was automatically derailed after passing a red signal outside Paddington at about 18:30 on Thursday evening, leaving two of the six lines into the station out of use.
Network Rail has said it will "await the conclusion of the official investigation" before commenting on the cause of the crash.
It said a limited service would run to and from London Paddington until the end of Friday, with timetables also affected over the weekend.
A spokesperson for Network Rail said in a statement: "Our priority plan is to enable Heathrow Express to run a full service, to reopen as many of platforms one to five as we can, to recover the derailed train, to repair the damaged infrastructure and restore full services."
They added: "It's a much more complicated situation than it may appear on the ground to passengers."
By Tom Edwards, transport correspondent, London
This incident will have been referred to the Rail Accident Investigation Branch and investigators will be trying to find out why the driver passed a signal at red.
The train was derailed by what are called "trap points" which have been part of the railway for well over a century. Experts say it is a fail safe so if the signal is at red, the points are set to shunt the train off the track to protect the main line.
What has made fixing the problem more complicated is the train hit a pylon supporting the overhead power lines. Those lines are now out of action reducing services.
Engineers will probably have to remove the pylon and then the derailed train and then fix the overhead wires. So it's a big job.
I'm told that probably won't happen on Friday and the best way to reduce the levels of disruption will be to start that work over the weekend."
Great Western Railway (GWR) is running more than half its services through the Thames Valley, but services are busier than normal.
A GWR spokesman apologised for the disruption caused and added: "We expect to run close to a full service over the weekend, with a small number of changes to the normal timetable."
Heathrow Connect services were suspended and Heathrow Express trains were only running every 30 minutes rather than the usual 15 minutes.
There are revised services between Paddington and Swansea, Penzance, Oxford, Greedford and Bedwyn.
Transport For London has allocated additional buses to affected routes.
No passengers were on board when the train derailed and there were no injuries.