Trains running between Colchester and Shenfield were delayed due to an incident.
Network Rail said emergency services were dealing with an incident between Colchester and Shenfield.
All lines have now been reopened.
A spokesman said: "Lines have reopened between Colchester and Shenfield as the emergency services are now safely clear of the line.
"Trains may continue to be delayed by 30 minutes or cancelled until 11:30."
Greater Anglia said the disruption is close to Chelmsford.
A spokesman said: "Due to emergency services dealing with an incident services are being disrupted.
"All services are currently stopped at Chelmsford whilst emergency services deal with [the incident]."
For updates on train services visit www.journeycheck.com/greateranglia/ or https://www.nationalrail.co.uk/service_disruptions/.
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