Rail services at the UK’s second busiest station are suspended after a person was struck by a train, Great Western Railway (GWR) said.
All lines serving London Paddington are blocked following the incident in the Slough area on Thursday morning.
The incident is affecting GWR and Elizabeth line services.
Disruption is expected to continue until 11am.
GWR said: “It is with great sadness that we report a person has been struck by a train, leading to all lines being blocked.
“It is necessary to bring all trains in the affected area to an immediate stop.”
The emergency services are at the scene.
London Paddington was closed for engineering work for the previous four days.
It was repeatedly affected by infrastructure faults in the preceding weeks.