The Govia-run Great Northern service is disrupted between Alexandra Palace and Welwyn Garden City due to an object being caught on the overhead electric wires.
The line is also having problems towards Hertford North, which will affect Cuffley-bound travellers.
Services could be delayed up to 15 minutes, according to Govia.
For more information on the incident please go here greatnorthernrail.com/travel-information/plan-your-journey/service-updates
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