France's national rail operator says it has finished repairing infrastructure damaged in a suspected coordinated arson attack on Friday, reports the BBC.
State-owned SNCF said most trains were running as planned on Sunday and full service will resume on Monday.
Police are still searching for the perpetrators behind what French ministers and officials have described as "sabotage" designed to paralyse high-speed TGV lines running to and from Paris.
Hundreds of thousands of people were caught up in the resulting disruption, which came hours before the opening ceremony of the Olympic Games in the capital.
SNCF said staff have been working around the clock to manually repair fibre optic cables, which were targeted on the North, Brittany and South-West lines.
Rail workers foiled an attempt to destroy safety equipment on a fourth line.