All rail lines between Reading and Slough are being affected after lightning damaged equipment.
Train services running to and from the stations may be cancelled or delayed at short notice.
Operator First Great Western said it will provide an estimate for when normal services will be resumed as soon as the problem has been fully assessed.
First Great Western tickets are being accepted on Chiltern Railways, Cross Country and London Underground services.
Buses are also transporting passengers to their destination until further notice.
Visit journeycheck.com/firstgreatwestern for more information.
Damage to equipment between Reading and Slough means that fewer trains are able to run on all lines.
As a result services running between the two stations could be cancelled delayed at the last minute.
There is no estimate as to when service will return to normal but will be provided as soon as an assessment is carried out and First Great Western have promised an update within the hour.
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