There are currently delays on the Chingford to Liverpool Street Overground line due to an earlier signalling problem at Liverpool Street.
Greater Anglia have said passengers should expect delays of up to 10 minutes and some trains may be cancelled at a short notice.
Trains services are expected to return to normal at 8:30am and tickets are being accepted on First Capital Connect, Central Line and Victoria Line routes, as well as local bus routes.
A normal service has now resumed on the Central Line in both directions following an earlier signal failure at Woodford station.
Greater Anglia has apologised and thanked commuters for their 'patience' and 'understanding'.