Public prosecutor Eric Maillaud said the child was only discovered when investigators gained access to the crime scene, almost twelve hours after a cyclist happened upon the carnage.
The father of a family slain in the French Alps was identified Thursday as Saad al-Hilli, a French police source said.
Confirming that the three victims in the BMW were from a family of British holidaymakers, he said: “She was hidden under the bodies for some eight hours and didn’t move for the whole time.”
The young survivor was speaking English when she was found, according to Sky sources.
The victims had still not been formally identified by 0900 GMT on Thursday. They were described by fellow campers as being of Middle Eastern appearance.
British consular officials were at the scene but the Foreign Office in London said it could not immediately confirm the identity of the victims or their nationality.
Chevaline and the surrounding area is popular with tourists and second homeowners from all over Europe, including many Britons.
The identity of a dead man described as the father of the family has been “almost certainly” established, while two female victims are yet to be formally identified, the Haute-Savoie prosecutor said.
The killings took place in a forested area near the village of Chevaline, near Lake Annecy, in the Haute-Savoie region.
The male victim was found at the wheel of the car, and the two dead women in the back – apparently covering the girl, four, who survived.
The girl’s elder sister, who was found shot next to the car, was in a serious but stable condition in hospital after being flown by helicopter to the nearby city of Grenoble
The body of a male cyclist was also found nearby.
The wounded girl is believed to be around seven years old and was shot at least three times, according to reports quoting police sources.
The four bodies and the BMW were riddled with bullets, the reports added.
Eric Maillaud, the prosecutor in charge of the investigation, said the four-year-old had emerged unscathed.
“She stayed, curled up under the bodies for eight hours and didn’t move in all that time,” he said.
The first police to arrive on the scene did not spot the girl and, with the car being left untouched and the area sealed off pending the arrival of forensic experts, she was left to endure a traumatic ordeal until she was finally discovered around midnight.
“It was only once we had access to the scene of the crime that we found her,” Maillaud said. “The little girl spoke English. She heard noises, shouts but she can’t tell us any more than that. She is only four years old.
“She is being looked after and we are doing everything we possibly can to care for her.”