A seven-hour breakdown of emergency phone line numbers in France was linked Thursday to possibly three deaths, leading to urgent investigations to determine the extent of the human cost.

Many people found themselves either unable to reach emergency medical, police or fire numbers, or had their calls cut off mid-conversation, from around 5 pm (1500 GMT) to midnight on Wednesday.

"It's too early to give you a toll, but obviously we are very concerned," President Emmanuel Macron told a voter in southwest France when asked if anyone had lost their life as a result of the turmoil.

Telecom operator Orange has acknowledged responsibility for the problems, with chief executive Stephane Richard offering his "deepest apologies" after being summoned to the interior ministry.

A formal investigation has been opened in the western Morbihan region after a 63-year-old man suffering from a heart problem died in hospital in the town of Vannes after being driven there by a relative.

The patient had been unable to call an ambulance on the usual number, a statement from the local government said.

Part of Orange's French network broke down for several hours
Part of Orange's French network broke down for several hours AFP / ERIC PIERMONT

Another two deaths of people with cardiovascular conditions on the island of La Reunion are also being investigated, Interior Minister Gerald Darmanin said.

The interruption came with France in the latter stages of its third wave of Covid-19 infections, with around 10,000 new cases and 134 deaths reported in the last 24 hours.

French numbers for emergency healthcare, police and fire services can be reached on 15, 17, and 18, as well as a universal European emergency line, 112.

Orange said that it suffered a problem with a router that receives calls to the shortened emergency numbers and transfers them to local call centres, which use regular 10-digit phone lines.

"We have no indication which leads us to think that it could be an external attack," CEO Richard told the TF1 channel, adding that the cause was most likely "software failure in critical network infrastructure".

Orange boss Stephane Richard was summoned by the government over the incident
Orange boss Stephane Richard was summoned by the government over the incident AFP / Thomas SAMSON

The company, which was formerly the state monopoly France Telecom, said its network had been functioning normally since midnight but was still being monitored, while alternative emergency numbers remained available.

Other regular Orange clients also experienced problems during the outage.

Darmanin, who cut short an official trip to Tunisia to handle the crisis, condemned "serious and unacceptable dysfunctions."

The French breakdown follows similar problems at Belgian operator Proximus in early January, which led to emergency numbers being disrupted for an entire night.

In June 2019, the Dutch national telecoms carrier KPN was to blame for a four-hour outage of the 112 emergency line, which is used by all 27 EU states alongside local numbers.

The year before, US telecoms group CenturyLink suffered a massive technical failure that affected ATM withdrawals, 911 calls and other services.

Medics in France said the disruption to ambulance services had caused chaos, with demand for emergency services tending to peak in the early evening.

"This caused mayhem in our organisation," Philippe Juvin, head of emergencies at the Georges-Pompidou hospital in Paris, told Radio Classique.

"But there was no panic, and we adapted fast, telling ourselves that it wouldn't last and that it would be fixed during the night," he said.

The head of the Samu-Urgences emergency medical services union, Francois Braun, said "people were unable to access the service, calls were not coming through, and others were cut off in the middle of a conversation."

Speaking during a visit to Tunisia, Prime Minister Jean Castex on Thursday called the outage "a significant event that we have taken seriously" and from which "we must draw all the necessary consequences."

Orange's competitors Bouygues and Altice, owner of SFR, said Thursday that they also logged reports of service failures, with sources at both companies ruling out foul play.