Many Great Anglia rail services across the east have been cancelled or delayed after a person was hit by a train between Chelmsford and Witham.
Services across Essex, Suffolk and Norfolk have been affected.
The company tweeted at 6:31am to warn passengers that there would be disruption on Monday morning.
Greater Anglia said that its tickets would be accepted on TFL services between Liverpool Street and Shenfield.
The rail operator said that services between Liverpool Street, Witham, Colchester, Ipswich and Norwich would be subject to short notice delays, alterations and cancellations.
Passengers are being urged to check before they travel to get the latest updates.