The overground line serving commuters from Chingford to Liverpool Street are being urged to seek an alternative route as the service is suspended for the rest of the day.
Damage to an overhead power line between St James Street station and Chingford earlier this morning has still not been repaired.
Greater Anglia has said a team of engineers for Network Rail will be carrying out repair work on the line for the remainder of today.
An earlier fault with the overhead line at Hackney Downs has now been resolved and a reduced service will now operate to Chestnut and Enfield.
Tickets will be accepted on all TfL buses between Liverpool Street and Chingford and on all reasonable London Underground routes.
Greater Anglia was unable to say how the damage was caused, and if the service will resume as normal tomorrow morning.
An Abellio Greater Anglia spokesman said:"Customers can obtain information on alternative travel arrangements from our website.
"Tickets are being accepted by London Buses and Underground routes. There are also delays of up to 15 minutes to some services in the Hackney Downs area because of a separate overhead power line fault.
"We would like to apologise to customers for the inconvenience caused."