Tänak, which is making its first race in Hyundai, was in fourth place ahead of the fourth special section, Saint-Clement-sur-Durance - Freissinieres, where the accident occurred after just over nine kilometers.
Tänak drove off at high speed into a ditch and the car then continued to roll for several turns. Both Ott Tänak and his map reader Martin Järevoja are reported to be okay and left the car on their own.
However, both have been taken to hospitals for a routine check.
Today's stage contains six special sections. Halfway through the day, Briton leads Elfyn Evans, 8.9 seconds ahead of Thierry Neuville. Sébastien Ogier, who won the Monte Carlo rally six times, is 9.7 seconds behind teammate Evans.
- The feeling in the car has been good and we made the right tire choice so a big thank you to the team for that. It has been great so far, says Elfyn Evans
WRC's reporter after finishing the last stretch of the morning.