Disruption is expected to rail services until 1pm due to a signalling problem between Chelmsford and Hatfield Peveral.
It has resulted in fewer trains being able to run on the line, with some services being cancelled or delayed by up to 10 mins.
Engineers are currently working on site and are expected to remain until 12noon.
Disruption is expected until 1pm.
The 11.18am service from London Liverpool Street to Clacton-On-Sea will call additionally at Hatfield Peverel.
The 12.52pm Ipswich to London Liverpool Street service will start at Colchester and no longer call at Ipswich and Manningtree.
The 11.48am London Liverpool Street to Braintree service and the 1pm service from Braintree to London Liverpool Street have both been cancelled.
The 12.33pm Ipswich to Braintree service will be replaced with a rail replacement bus, calling at Braintree Freeport and Braintree.
There will also be a mini bus calling at all stations between Witham to Braintree.
The 1pm Braintree to Witham service will be replaced with a rail replacement bus, calling Braintree Freeport and Witham, with a mini bus calling at all stations between Braintree and Witham.
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