A person has been hit at Reading West Station, leading to disrupted services to Newbury and Basingstoke.
A statement on FGW's website - made before 8pm - said passengers could be waiting up to an hour longer to finish their journeys.
It read: "Trains are currently unable to run through Reading West, journey times may be extended by up to 60 minutes.
"CrossCountry services between Reading and Southampton are diverting via Guildford and not calling at Basingstoke, Winchester and Southampton Airport Parkway. Passengers for these stations are advised to travel to Southampton and change onto a South West Trains service.
There is no firm estimate yet of how long disruption will last but it is likely to continue until at least 22:00."
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