A body on the line is causing severe train delays between Oxford and London Paddington this morning.
At about 6.30am a person was seen lying on the tracks between Taplow and Burnham in Berkshire.
The area was sealed off as scenes-of-crime police officers investigated the scene.
The mainline has now re-opened and the relief line is expected to be back up and running very soon, Network Rail said.
A spokesman said: “We had a call at 6.30am from a driver who reported a suspected body by the side of the railway and that was confirmed by the next driver through.
“We contacted British Transport Police and the mainline and relief line were closed so officers could access the scene.
“The mainline has now re-opened and the relief line is expected to be open within minutes, but there will still be some residual delays.”
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