There is disruption on First Great Western between Worcester Shrub Hill and Swindon, and between Worcester Shrub Hill and Oxford because of a derailed train.
Some lines are now blocked as the train is re-railed which could take up until 2.30pm.
Replacement buses are running between Worchester Shrub Hill and Cheltenham and journeys will be delayed by up to half an hour.
More top news
Saturday morning's weather for the east of the region
Saturday morning's weather for the west of the region
Man jailed for leaving another needing metal jaw plates after unprovoked attack