There's a reduced service on the First Great Western line between Bristol and London Paddington.
Trains are being diverted via Newbury, and services are suspended between Cheltenham at Paddington, with replacement buses in place between Swindon and Didcot; Swindon and Gloucester; and Bath and Swindon.
More top news
Becky Watts' uncle speaks exclusively to ITV News following the arrest of two people on suspicion of her alleged kidnap and murder.
The killer serving life for the murder of Jo Yeates has been sentenced to a further 10 months after admitting possessing child abuse images.
Meet the twins from Gloucester who've had to produce their birth certificates to friends in order to prove that they are in fact related.