The woman aged in her 30s was taken in questioning on Tuesday, and had initially only been suspected of involvement in the death of an 84-year-old resident of a retirement home in Chambery, near the French Alps.

However, the case took a dramatic turn on Thursday afternoon, when it emerged that the suspect had been formally arrested on suspicioon of poisoning five more pensioners at the care home.

“The suspected admitted she had wanted to relieve the suffering of six people who died since October,” a source close to the inquiry told French TV TF1.

“She did not admit intending to kill them,” the source added.

The alarm was raised by management at the retirement home, in the department of Savoie, after one female resident, who had been given a clean bill of health by doctors, suddenly lapsed into a coma, and died two days later, on November 29^th.

Judicial police in the area opened an investigation into possible “administering of a harmful substance,” and interrogated the care home employee on Tuesday and Wednesday.

Earlier in the week, a source close to the inquiry told French radio RTL that, aside from the death of this 84-year-old woman, investigators were also looking into several other “troubling” circumstances at the establishment.

Management at the retirement home did not comment formally on the case, but an anonymous representative told RTL the situation was one of “real seriousness.”