Train services from London to Stansted Airport are returning to normal, after overhead wire problems caused the line's closure.
Disruption could last until 3.30pm, but services between the capital and the busy airport have restarted.
Stansted Express, which runs trains between the capital and the airport, said: "All lines have now reopened in the Cheshunt area after earlier overhead wire problems. Greater Anglia and Stansted Express service are now resuming on all routes from Liverpool Street to Hertford East, Stansted Airport and Cambridge and between Stratford and Bishops Stortford."
But passengers have been warned there could still be cancellations, delays and alterations. The replacement bus routes which had been laid on is no longer available.
The company added: "We are sorry for the disruption to your travel plans caused by this incident and thank you for your patience and understanding."