Commuters have faced travel disruption after a landslide blocked a railway between Coventry and Rugby.
Earth fell on to the tracks on Sunday afternoon causing train cancellations and diversions on routes between Birmingham and London Euston.
London Northwestern Railway (LNR) services are only running between Birmingham and Coventry, and Northampton and Euston.
Disruption is expected to continue into Tuesday.
Rail replacement services running between Coventry and Northampton have been put in place.
Engineers are working to cut back and clear vegetation from the railway embankment.
This "critical" task would help workers to understand the scale of the damage and to check that there was no risk of further landslips, Network Rail said.
A second operator, Avanti West Coast, said its southbound services on the route had been diverted and may be subject to cancellations and delays.
LNR said while northbound train services could still operate, a reduced timetable was expected.
Avanti advised passengers travelling north from London to Birmingham that while services were running, they may be subject to short-notice delays.
Both operators have issued apologies to passengers.
Jonny Wiseman, LNR customer experience director, said: "This landslip has resulted in a significant amount of earth movement next to the railway, meaning it is not safe to run trains through the area until Network Rail has completed emergency earthworks."