The incident occurred near Southall in London, affecting routes between Paddington, Heathrow Airport, and Slough.
Delays of up to 20 minutes or alterations to services are expected to continue until 11am.
Three train operators are affected by the disruption, including the Elizabeth line, Great Western Railway and Heathrow Express.
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A safety inspection of the track near Southall is causing disruption between London Paddington and Slough.
To help ease the disruption, passengers on the Elizabeth line can use their tickets at no extra cost on Great Western Railway services between Paddington and Reading, and on South Western Railway services between Waterloo and Reading.
London Buses between Paddington and Hayes and Harlington or Heathrow Airport, as well as local buses between Hayes and Harlington and Reading, are also accepting tickets.
GWR customers can use Elizabeth line services via any reasonable route.
Passengers who are delayed may be entitled to compensation and should keep their train ticket and make a note of their journey to support any claim.