The gendarmerie is investigating the death of three-month-old twin girls.
The infants were taken care of by the emergency services in Lamarque in the Médoc (Gironde), Monday.
When they arrived, the babies were unconscious.
One of the girls died on the spot despite attempts at resuscitation.
The other, transferred to CHU Pellegrin in Bordeaux, died a few hours later, reports France Bleu Gironde.
The gendarmes are trying to determine the circumstances of these two deaths.
A woman, a relative of the twins, was placed in police custody late Thursday morning, it was extended.
The Bordeaux prosecutor's office has opened an investigation for intentional homicide.
Miscellaneous facts
Finistère: In Carantec, the two girls were asphyxiated and their mother strangled
Company
Saint-Etienne: A young father suspected of having defenestrated his two little girls
Gironde
Aquitaine
Babe
Miscellaneous facts
Survey
Gendarmerie
Constable
Bordeaux