A signalling system fault has been causing disruption to trains at Thetford on Friday afternoon.
Greater Anglia has said some lines are blocked between Thetford and Lakenheath.
A statement by the operator says: "Train services running through these stations may be cancelled, delayed or revised. Disruption is expected until further notice.
"Greater Anglia and Network Rail are sorry if your journey has been affected by this disruption."
Disruption is expected until 2.45pm with train services through Thetford returning to normal.
Train services between Norwich and Stansted Airport have also been disrupted due to the earlier signalling problem.
Greater Anglia has said the signals have been restored and train services are running as normal. The 12.29 Norwich to Stansted service was running 19 minutes late and terminated at Cambridge.
The 2.48pm Stansted to Norwich service will start from Cambridge as a result.
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