A French doctor already charged in the poisoning of seven patients was brought before a judge Thursday on suspicions he may have poisoned 17 others at a clinic in eastern France, prosecutors said.

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

This week he was brought in for questioning over 66 more suspicious cases of cardiac arrest during operations on patients otherwise considered at low risk of such incidents.

"Seventeen cases have been retained" involving patients aged 4 to 80, of whom seven died after doctors were unable to revive them, local prosecutor Etienne Manteaux told a press conference.

Pechier has been brought before a judge who will determine if he is charged, and Manteaux has asked that he be jailed pending further investigations.

Pechier was "the common denominator" in the new cases, which occurred at a time when he was in open conflict with fellow anaesthesiologists at the Saint-Vincent clinic in Besancon, Manteaux said.

"He was most often found close to the operating bloc" when the cases occurred, and made quick diagnoses of the problem and the action to take, "even when nothing allowed anyone to suspect an overdose of potassium or local anesthesia," he said. 

Prosecutors have alleged he may have tampered with his colleagues' anaesthesia pouches 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.

During questioning this week, Manteaux said Pechier acknowledged that criminal acts had taken place at Saint-Vincent, but that "he was not responsible for these poisonings."