Trains between Cambridge and Ipswich have been suspended due to a signalling problem at Newmarket.
Great Anglia has warned services could be delayed or cancelled until at least 6pm today (Thursday).
Greater Anglia is hiring additional trains for Essex commuter services.
It's to improve service reliability while others are being refurbished.
£8m is being invested to provide WiFi, more comfortable seating and install new heating systems.
An Essex MP has written to the Transport secretary saying he is 'fed up to the back teeth' with disruption on the mainline to London.
Sir Simon Burns - the MP for Chelmsford - said the delays on the Chelmsford to Liverpool street services due to overrunning engineering work is totally unacceptable.
"I accept it is important that badly needed engineering work is carried out to improve and enhance the railway infrastructure on the London Liverpool Street - Chelmsford - Ipswich line, but the price we have to pay for this welcome investment and the improvements it will bring, should not be at the expense of overrunning engineering works and a total disruption to the service."
Train operator Abellio Greater Anglia says services between Norwich and Cambridge and Peterborough are likely to be disrupted until the end of the today.
The problems follow the derailment of a freight train at Wymondham earlier today.
Services are currently beginning and terminating at Thetford with a bus service on to Norwich. But it's adding an hour to journey times.
Train services between Norwich and Peterborough and Cambridge have been suspended after a freight train was derailed at Wymondham.
Trainer operator Abellio Greater Anglia says it doesn't know when normal services will resume.
Plans to electrify the Midland mainline rail route between Bedford and the East Midlands have been put on hold by the Government.
The Transport Secretary Patrick McLoughlin told MPs the planned upgrade is being paused to allow Network Rail to concentrate on other projects
The Conservatives had promised the electrification would be completed by 2020 and even had a pledge in their General Election manifesto.
Click below to watch a report by ITV News Anglia's Political Correspondent Emma Hutchinson
Kettering MP Philip Hollobone says pause in electricfication of Midland main line is "not good news" for his constituency
Wellingborough MP Peter Bone says constituents will be disappointed with pause in electrification of Midland Main line
A £38 billion five year plan to overhaul Britain's railways is being "reset" because it is "costing more and taking longer", Transport Secretary Patrick McLoughlin has told MPs.
Electrification work will be "paused" on the Midland mainline.
"On the Midland mainline, better services can be delivered on that line before electrification with things such as speed improvement works.
"So work on electrification will be paused. I want it to be done and done well. It will be part of our future plans for the route.
Transport Sec announces work on electricfication of the Midland main line will be paused but remains a plan for future
Electrification of Midland mainline between Bedford & Sheffield via Kettering a Conservative manifesto promise, now that work will be paused
Rail passenger satisfaction levels have dipped particularly on the trains run by Abellio Greater Anglia in the East of England.Read the full story ›
Rail passenger satisfaction levels have dipped particularly on the trains run by Abellio Greater Anglia in the East of England.
The proportion of passengers satisfied with their journey overall has fallen from 82% in spring 2014 to 80% in spring 2015, a survey of 31,000 rail travellers by Transport Focus (formerly Passenger Focus) showed.
The satisfaction rating for Greater Anglia was at 75% down from 80% in autumn 2014. Among the higher scorers was East Coast with 94% of passengers satisfied.