The bones of five infants were found in southeastern France, in the home of a couple who had just welcomed a baby, which is reported to be in excellent health, according to local authorities.

The mother’s partner was the one who made the grim discovery, according to the prosecutor’s office, which announced that it had opened a preliminary investigation into the alleged murder of a child under the age of 15.

According to the authorities, the woman gave birth at home on Sunday and was then taken to hospital. Her partner reportedly became concerned after realizing—only very late—that she had been pregnant, and began searching their apartment in the city of Orange, where he found what appeared to be human remains.

The 32-year-old man “became concerned after learning about his partner’s pregnancy at a very late stage. She gave birth (on Sunday) at their home and was then taken to hospital.”

Left alone in the house, he began searching and discovered “what appeared to be human remains.” He alerted the hospital in Orange, which in turn reported the matter to the prosecutor’s office.

Police searched the home, an apartment in central Orange, on Monday evening.

A forensic pathologist determined that the bones and decomposed bodies found belonged to five infants, the prosecutor’s office said, confirming information from sources close to the investigation. An autopsy and forensic examination of the remains are expected to be conducted.

The mother, who is also 32 years old, has not yet been questioned by prosecutors.

The couple also have two other children, aged eight and nine, and live on the second floor of an old building a short distance from the ancient theatre of Orange.

One of their neighbors, Philippe Constant, told Agence France-Presse that he was awakened at 11:00 p.m. on Monday when police officers rang his doorbell while looking for the couple’s apartment.

Another neighbor, who lives on a nearby street, described them as a “charming” couple who had lived in the building for about two years and had two children attending primary school. “They were ordinary people. The mother would pick up the children from school at lunchtime so they could eat,” while the father “left for work in the morning and returned in the evening.”

Infanticide is not uncommon in France and is often attributed to the mother’s “partial loss of judgment” or to “pregnancy denial,” in which women conceal their pregnancy from those around them.

In the most serious of these cases, Dominique Cottrez, a former nurse, killed eight newborn babies and buried them in her parents’ garden and in the garage of her own home.

Their remains were discovered in 2010, and five years later Cottrez, who was then 51 years old, was sentenced to nine years in prison.