FOUR members of a family were discovered dead, with the sole survivor seriously injured, after they allegedly jumped off a balcony.

Police were called to the scene in Montreux, Switzerland, after reports of five people jumping from a building next to a casino.

According to Le Temps, the only survivor of the mystery is a 15-year-old boy who was hospitalised with catastrophic injuries.

According to Vaud police, the victims were a 40-year-old man, his 41-year-old wife, their 8-year-old daughter, and the woman’s 41-year-old twin sister.

Formal identification is “still being worked on,” but cops have confirmed that the five are members of the same French national family.

Several interviewed neighbours in the area stated that the incident occurred around 6 a.m.

One neighbour claimed to have seen three bodies on one side and two on the other.

“I thought it was a bad film; I couldn’t look at the image for more than a few seconds,” he said.

Another witness who arrived at the scene before the police arrived stated that the people were lying on the ground without shoes.

According to Vaud police spokesman Alexandre Bisenz, the group appears to have “visibly thrown themselves into the void from an apartment,” landing hard on the pavement below, where they were discovered by passers-by.

Apart from them, police confirmed that there were no other people in the apartment.

The tragedy occurred after two officers went to the apartment “to execute an arrest warrant issued by the prefecture in connection with the home schooling of a child,” according to a police press release issued around 1pm.

When the cops knocked on the door, they heard a voice asking who was there, but then there was no more noise from inside the apartment.

They left the premises after being unable to make contact, but in the meantime, a witness called the police to report that “people had fallen from the balcony of an apartment.”

Katia, 35, stated to Blick: “The noise of the police, who arrived racing with a large number of emergency vehicles, woke me up. We have a Whatsapp group with our neighbours, and everyone thought there was a casino raid.”

Rosa, her 66-year-old colleague, stated: “I’ve been in the area for 32 years and have never seen anything like it. I reasoned that it could be someone I know. It’s a family, according to everyone.”

One neighbour described the three-year-old family as “inconspicuous” and “very low key.”

“You didn’t hear anything from them, your father never greeted you in the hallway, and he ordered a lot of packages almost every day.”

He did, however, claim that he had noticed a strong odour of incense sticks for a few days prior to the incident.

Police have not confirmed whether the jumpers were members of that family, but an investigation is underway.

Dozens of police officers and a special forensic unit were on the scene, cordoning off the crime scene while they collected evidence, inspected the balconies, and searched for clues with a police dog.