Passengers travelling between Oxford and Worcester Shrub Hill are currently experiencing delays.
Emergency engineering works have been taking place at Honeybourne after problems with a culvert, which started at around 4pm.
Tickets are being accepted on CrossCountry and London Midland services.
James Davis, spokesman for First Great Western, said: “My understanding is that a culvert in Honeybourne prevented services going through the area.
“That has now been sorted and trains were going through at a reduced speed.
“Things should be running as normal now but as the incident happened during peak time and that has had a knock on effect.”
Trains have now resumed, but may be severely delayed while the service returns to normal.
Disruption is expected to continue until about 9.15pm.