French police have arrested a care worker accused of poisoning to death six pensioners at a retirement home in the Rhône-Alpes region of south-eastern France

The 30-year-old woman reportedly told investigators she administered a lethal cocktail of drugs to the six guests at the Césalet home in Jacob-Bellecombette near Chambery, as they were very old or in very bad health.

"The suspect admitted she wanted to relieve the suffering of six people who died since October," a source close to the investigation told AFP. "She doesn't admit the intention to kill."

The care worker confessed the poisonings after police questioned her in relation to the death of an 84-year-old woman who died at the end of November.

The death had aroused the suspicion of the medical staff at the retirement house.

The elder woman, who had a clean bill of health, had suddenly fallen into coma, dying two days later at a local hospital.

An autopsy revealed an overdose of psychotropic substances, which she had not been prescribed.

Le Parisien newspaper reported the 30-year-old told police she acted in the wake of her mother's death, which was said to have happened "in very hard circumstances".

Authorities have opened an investigation into over the alleged "administration of harmful substances".