A lightning strike has damaged equipment causing severe delays to First Great Western trains.
Services between Reading and Slough are facing delays and possible cancellations.
Services are running from Oxford and Banbury through to London Marylebone.
Passengers travelling between Oxford and Banbury in both directions can use Cross Country services.
Ticket restrictions have also been lifted enabling passengers to board Chiltern Railways services to Oxford and Banbury.
Our top stories
- Sexual assaults are denied
- Authorities search for solutions as graffiti in Oxford doubles in a year
- Tackling cyber-crime and fraud are main priorities for Conservative police commissioner candidate
- Prime Minister says he has no offshore funds following Panama Papers leak
- Traders called on to support this summer's Cowley Road Carnival
- Tributes paid in Witney to former butcher and much-loved member of community
- Successful education scheme from Oxford charity to be rolled out across the UK
- Stunt actor from Oxford meets his match on Take Me Out
- 11 years on, pupils jump for joy over installation of crossing
- Barton gets £4m cash boost to transform estate’s homes and shops
- Time-travelling story takes top spot in our Ox Tales competition
- Former Oxford City director Thomas Guerriero pleads guilty to $6.6m fraud
- Police confirm dead baby was newborn and renew desperate appeal to find mother
- Adam says yes after reading girlfriend's Leap Day proposal on the Oxford Mail website