Services in both directions between Chingford and Liverpool Street are expected to be disrupted until the evening rush hour begins.
Due to a broken down train between Highams Park and Wood Street earlier today, Greater Anglia have said trains may be cancelled, delayed or revised at short notice.
Despite engineers efforts to fix the train and re-open the line, disruption is exptected until 5pm.
London Underground and TfL buses will continue to accept tickets on any reasonable route until further notice.
As a result of this afternoon's disruption, some services between London and Enfield Town and between London and Cheshunt, and London and Hertford East will be impacted.
Greater Anglia said: "We thank you for your continued patience whilst this broken down train has been recovered and the train service is restored to normal."