Software failure is being blamed for the breakdown which put emergency phone numbers out of action and is suspected of causing at least three deaths.
ADVERTISEMENTFrance's major telecom operator Orange has apologised for an "extremely rare" outage which put emergency numbers out of order across France.
The unprecedented breakdown, which began on Wednesday and continued into Thursday in parts of the country, has been provisionally linked to at least three deaths.
Stéphane Richard -- CEO of the French multinational, the fourth largest in Europe -- has ruled out the possibility of a cyberattack. On Thursday he said the root cause was probably software failure in vital network equipment.
The company told AFP that a "technical incident on a router had greatly disrupted VoIP (voice over internet protocol), internet calls in some regions".
According to the French interior ministry, standard two-digit phone numbers for ambulance, police and fire services -- as well as the pan-European 112 number -- were out of action or very hard to access across France for several hours from late afternoon on Wednesday.
A crisis unit set up by the ministry published lists of alternative emergency numbers for people to call, which it says will continue to operate until Friday morning.
Health Minister Olivier Véran said on Thursday that around ten regions were still affected by the breakdown. Interior Minister Gérard Darmanin slammed "serious and unacceptable malfunctions", citing three deaths from heart attacks.
Prosecutors at Vannes in southern Brittany have opened an investigation following the death of a 63-year-old man in the town hospital's casualty department.
President Emmanuel Macron, visiting southwestern France, said it was too early to assess the extent of the damage, adding that "obviously we are very worried".
The crisis cell was due to meet in the early evening on Thursday to assess the situation.