The 102-year-old woman, who has been transferred to a psychiatric hospital, allegedly told a staff member at the retirement home where the two lived that she had "killed someone", according to the BBC.
BBC reported on Thursday that the 102-year-old is now in a psychiatric hospital.
She was arrested and sent to psychiatric care after another woman was found dead in bed on Saturday at the home in Chézy-sur-Marne, 60 miles northeast of Paris.
"The resident of the neighbouring room, aged 102, appeared in great agitation and told one of the medical staff that she had "killed someone", he added in the statement late on Wednesday.
An autopsy revealed the 92-year-old had died from strangulation and significant blows to the head.
Prosecutor Frederic Trinh told AFP news agency that the suspect will undergo a psychological examination to determine whether she can be held criminally responsible for her neighbor's death. This media house does not correct any spelling or grammatical error within press releases and commentaries.