Four members of the same family died in the Swiss resort of Montreux on Thursday, and a fifth is in a serious condition, after they fell from a seventh floor balcony, police said.

       The dead include a man aged 40, his wife and her twin sister, 41, and their eight-year-old girl. The couple's 15-year-old son survived the fall and formal identification is now under way. Police said the victims were all French citizens.

       Unconfirmed reports in Swiss media, citing an unidentified police official, claimed the five had jumped from their apartment building.

       The group were found at about 7am on Thursday outside a building near the city’s Casino Barriere.

       Police said officers had gone to the apartment with a warrant for the father related to the home-schooling of one of the two children.

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       Swiss newspaper Blick reported that it was customary in the canton of Vaud for the school to carry out a check once a year to see if the home teaching guidelines were being complied with.

       Officers returned later after a witness notified them that people had fallen from a balcony, police said.

       Police investigate at the scene of the tragedy

       (EPA)

       "Unable to make contact with the possible occupants, they left the place," police said. "In the meantime, a witness called the police to report that people had fallen from the balcony of an apartment."

       The statement added: "Five members of the same family fell... from the balcony of their apartment in Montreux located on the seventh floor of a building on the street of the casino.

       “A man, two women and a young girl died and an adolescent has been hospitalised in serious condition.”

       The building where four members of a French family plunged to their deaths

       (AFP via Getty Images)

       White flowers were left next to the family’s apartment building

       (AFP via Getty Images)

       Police and emergency teams erected white tents at the scene, and forensics investigators were spotted on the top balcony of the building. The public prosecutor's office has also initiated an investigation.

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       Montreux is a lakeside city best known as a tourist hot spot and in particular for its annual jazz festival.

       Additional reporting by agencies