St Albans City Station. Picture: Danny Loo. (Image: Archant)
Trespassers on the railway line between St Albans and London St Pancras International are causing delays.
Services may be up to 15 minutes late and the disruption is expected to last until 4.30pm.
British Transport Police and Network Rail are on their way to the incident, which is in the Mill Hill Broadway area.
To follow the incident on Twitter, use #MillHillBroadway.
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