Engineers are working to repair an unstable embankment on the main rail line between London and East Anglia.
According to Network Rail, a "dip in the tracks" was found near Ingatestone on Thursday, 21 January.
It is affecting Greater Anglia services out of London Liverpool Street towards Essex, Suffolk and Norfolk.
Passengers coming from the capital need to use the Central Line as far as Newbury Park and then get a rail replacement bus to Witham.
Network Rail have warned passengers there may be ongoing disruption on Monday, and have advised people to check before they travel.
Ellie Burrows, Network Rail’s route director for Anglia, said: "Our teams have been on site since Thursday night and we will be working 24/7 to reopen the line as soon as it is safe to do so.
"I am sorry for the disruption this will cause to passengers. While we’ll try and keep noise to a minimum, some this work to rectify the embankment will be noisy. I am sorry if this disturbs those living close by."
The coronavirus lockdown rules state that only essential journeys must be made using public transport.