Work to stabilise part of the East Coast Main Line after a landslip will go into next week, transport bosses have said.
Trains between Darlington and Newcastle have faced disruption after part of an embankment at Aycliffe came away on Wednesday.
Rail operators apologised for the disruption and urged passengers to check timetables before they travel.
Network Rail estimates services will return to normal by Tuesday.
The landslip, which occurred on the northbound side of the line, saw ballast stripped from the land near the tracks.
It caused significant delays and cancellations to LNER, Transpennine Express and Crosscountry services.
Some trains have had to be started from railway stations further south along the line, including at York.
ℹ️#LNERUpdate Due to a landslip
11/11/23 The 04:45 #Newcastle to #KingsCross due 08:10 will be started from #York.
Tickets are valid on the LNER service after this train.
Customers are advised to travel on the 0526 LNER departure from Newcastle.
— London North Eastern Railway (@LNER) November 10, 2023
Remedial work is taking place in order to strengthen the embankment with the installation of steel piles. Much of the it will be carried out overnight when passenger trains are not running.
Network Rail said: "Our engineers are working flat out to restore train services back to normality as quickly and as safely as possible on the East Coast Main Line near Darlington.
"While a limited service is continuing to operate, I know this work is disruptive and I am sorry for the inconvenience this is causing to passengers. I want to thank them for their patience and understanding."
The line between Darlington and Newcastle has been closed, but the line from Newcastle to Darlington remains open, meaning there are restrictions on services operating in both directions.