A TfL Rail train. Picture: Hammersfan/Wikimedia Commons (Image: Creative Commons - must be attributed)
A speed restriction at Ilford is delaying trains between Shenfield and Liverpool Street in both directions by up to 30 minutes.
Services are also being delayed between Liverpool Street and Stratford by a defective train near Stratford.
On Twitter, a Greater Anglia spokesman warned that train services may be cancelled and that the delay was expected to continue until 11am.
National Rail engineers are on the scene working to resolve the problem.
Greater Anglia passengers can claim compensation here if your journey was delayed by 30 minutes or more.
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