Stephane Richard, the head of France's biggest telecoms operator Orange, has launched an internal inquiry into this week's network outage which prevented emergency phone calls in France.
Orange added the conclusions from this report should arrive within seven days time and that its teams remained mobilised and would continue to scrutinise the situation closely.
It reiterated that the network was operating normally again.
Health minister Olivier Veran said it was too soon to say whether there was any link between the outage and three to four deaths recorded during the period.
The incident has put Richard under political pressure, with President Emmanuel Macron saying he was "very concerned" by the incident.
The French government and state bank Bpifrance together hold around 23% of Orange's share capital, making the French state Orange's biggest individual shareholder.
The disruption to French emergency phone services had begun on Wednesday afternoon, before later easing and then being entirely fixed over the course of Thursday.
Richard has said the outage was not caused by an attack nor by a malicious act, while adding it could not be linked to a human error nor to a maintenance issue.