Anarchist groups have claimed responsibility for the sabotage that caused a blackout that affected the Cannes Film Festival for several hours.
Several prosecutors in the region are investigating a message of justification sent on Sunday to an internet discussion forum to verify its authenticity, French public radio and television reported.
An arson attack hit a high-voltage power pole on Saturday morning, and almost simultaneously, three of the four feet of a high-voltage pylon that supplies the city of Cannes were cut, causing it to fall and disrupting the power supply.
Some 160,000 homes lost power, but not the Festival Palais, which has its own generators, prompting festival organisers to send out a message of calm from the outset that the awards ceremony would not be affected.
Rail service was also disrupted and firefighters had to make a hundred calls, mainly to rescue people trapped in elevators.
Power was restored to most of Cannes after about five hours.
In the early hours of Sunday morning, a third act of sabotage in the form of an arson attack on another high-voltage pylon left 45,000 homes in and around the city of Nice without power.
Sources in the investigation insisted that the three sabotages required a group of people, as they could not be the work of a single individual, given the necessary technical expertise.
