Workers have discovered a dead body on the railway line near Swindon.
Emergency services were called to the tracks in the Shrivenham area at around 1pm this afternoon (Thursday).
Railway workers are understood to have found a deceased person, who is thought to have been hit by a train sometime earlier.
Trains between Bristol Temple Meads and London Paddington have been halted while 999 crews attend the scene.
Services calling at Swindon and Didcot are likely to be cancelled.
In a statement, a Great Western Railway spokesperson said: “Due to the emergency services dealing with an incident between Swindon and Didcot Parkway the line is blocked.
“Train services running through these stations may be cancelled, delayed or diverted. Disruption is expected until 15:15 26/09.
“We’re working with Network Rail and the emergency services to deal with an incident between Swindon and Didcot Parkway as sensitively, quickly and safely as possible.
“Your journey is likely to be severely delayed and take up to 90 minutes extra to complete. Some trains will be revised, only completing parts of their normal journeys. There will also be some cancellations.
“We are trying to source replacement transport to run between Swindon and Didcot Parkway, and will provide further details once this is confirmed.
“If you have been affected by this incident or you know someone else who needs support, there is always someone to talk to. Contact a Samaritan on 116 123 for free, any time, on any phone. Help is only a phone call away.
“We’d like to thank you for bearing with us, and we’re sorry for any disruption caused to your day.”