France began searching for answers Thursday after its emergency phone line broke down for several hours a day earlier.
It was too soon to say whether there was any link between the outage and three to four deaths recorded during this time, Health Minister Olivier Veran said on Thursday.
French President Emmanuel Macron also said that it was too early to draw conclusions, but that the situation was worrying.
Deaths during emergency line disruption
The disruption began at around 5 p.m. (1500 UTC) until midnight on Wednesday. Around a fifth of all people making calls to emergency medical, police or fire numbers in this period did not get through or had their calls cut off mid-conversation.
A person suffering from a cardiovascular disease is reported to have died in Brittany because the emergency services could not be reached in time. Prosecutors in Vannes, Brittany, announced they would launch an inquiry into the death.
The death of a 2-year-old toddler in the nearby Vendee region is also being investigated.
Two other people with cardiovascular diseases died on the island of La Reunion who had tried to reach emergency services, but it was unclear if their deaths occurred because medics did not arrive in time, Interior Minister Gerald Darmanin said.
Government demands answers
Darmanin, who dubbed the glitch "serious and unacceptable," summoned national telecom operator Orange's chief Stephane Richard on Thursday to explain the breakdown.
Richard offered his "deepest apologies" but said the cause of the outage remains unclear.
"We have no indication which leads us to think that it could be an external attack," CEO Richard told TF1 television. The cause was most likely "software failure in critical network infrastructure," Richard added.
The minister for digital affairs, Cedric O, said the state, which is Orange's biggest shareholder, will launch an investigation into the causes of the outage.
Back up and running?
Orange said its network had been functioning normally since midnight on Wednesday, but problems were still being reported from around a dozen areas in France on Thursday, according to the health minister.
Interior Minister Darmanin said issues could persist until Friday morning.
kmm/rs (AFP, Reuters, dpa)