The three workers remain in hospital after falling up to 20ft
A railway line linking London to East Anglia, beset by major delays over the past few days, has faced new problems after a freight train derailed.
National Express East Anglia services between Colchester and Marks Tey have been hit by delays of up to 45 minutes after the derailment in the afternoon.
Network Rail said replacement bus services between Colchester and Witham were being brought in.
There had been no estimate as to when normal services would be resumed.
The route affected runs from London Liverpool Street to Norwich, via Ipswich and Colchester.
Earlier there had been disruption on the line while repair work was carried out on overhead cables which came down near Ingatestone in Essex on Monday.
Three workers were injured while carrying out the repairs to the power cables on the line on Wednesday night.
They fell up to 20ft to the ground from an elevated platform and were kept in hospital overnight.
The East of England Ambulance Service said one man had suffered head and chest injuries and another suffered minor leg injuries.
A third man, who suffered head injuries, was flown to Queen's Hospital, Romford.
British Transport Police said an investigation was under way.
Essex County Council said on Thursday that it wanted "urgent talks" with Network Rail and National Express East Anglia.
Norman Hume, the council's Cabinet member for highways and transportation, said: "I am disappointed that commuters in Essex have been left suffering in these miserable conditions.
"Already I have heard some terrible stories of commuters suffering at stations and on trains as they try to get to and from work.
"Although I accept these works were of an emergency nature rather than planned, I will be looking to find out the causes from Network Rail and asking whether commuters have been given the best service possible as they tried to carry out their journeys."