First Great Western services between London Paddington and south Wales have been disrupted after a person was hit by a train at Ealing Broadway.
Services may be cancelled or delayed by up to 45 minutes at short notice, said the train operator.
Fans returning to west Wales by train on Sunday already faced up to 75 minutes added to journey times.
Engineering work meant First Great Western and Arriva Trains Wales services were suspended between Cardiff and west Wales with buses running instead.
Wales beat France 16-6 on Saturday, their first win in this year's Six Nations.
Wales rugby fans coming home by train following the Six Nations win over France in Paris could face long delays.