The incident occurred earlier this morning between Colchester and Chelmsford.
A spokeswoman for Greater Anglia, who run the service between Norwich and London Liverpool Street, said: “Regrettably, due to a person being hit by a train between Colchester and Chelmsford, services will be disrupted.
“Train services running through these stations will be cancelled, delayed or revised. Disruption is expected until further notice.”
One Norwich commuter said he is stuck at Chelmsford.
Passengers on the service had already faced delays earlier this morning after reports of a fire by the tracks in Chelmsford.
Trains had been hit with delays of around 20 minutes.