The First Capital Connect (FCC) service travelling from St Albans to London St Pancras will be suspended for the rest of the day.
Overhead wire problems are causing disruption at Hendon and trains will not run between Luton and London St Pancras.
Network Rail is currently on site assessing the problem and it is thought the cancellations will be in place for the rest of the day.
A spokesman from FCC said a UNO bus service travelling between St Albans and Hatfield is currently in place.
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