Some Léman Express services will be disrupted for the rest of the week after a landslide covered the tracks near the Reignier-Esery station in Haute-Savoie.
The main lines affected are the L2 and L3 – running to Annemasse and Annecy.
A bus replacement service is linking some stations.
Authorities say services should start to return to normal from Friday. They point out the landslide has caused significant track damage.