Frederic Pechier worked as an anaesthesiologist at two private clinics in Besancon, eastern France, when seven patients, aged 37 to 53, went into cardiac arrest from 2008 to 2017.

Two of the patients died while the others were resuscitated. Investigators later found lethal doses of potassium in their blood.

Pechier, who was first charged in May 2017, has denied the allegations and was released pending trial.

Investigators claim that Pechier created emergency situations so he could show off his skills at resuscitation. Photo: AFP

The two-year inquiry has led police to expand their focus to “around 50 reports of unwanted events,” medical jargon for unexpected complications or deaths among patients otherwise considered healthy, the source said.

Pechier's peers considered him a brilliant anaesthesiologist, and while he was not in charge of sedating the seven patients that sparked the inquiry, his quick diagnostics for resuscitation raised suspicions for investigators.

Prosecutors have alleged he may have tampered with his colleagues' equipment to create operating room emergencies where he could then intervene to show off his supposed talents.

Pechier's lawyers have denied the claims, and in November they accused police of altering declarations he made during his initial questioning.