A diamond necklace worth 2 million euros disappeared during a star-studded party at the Cannes film festival on Tuesday.
De Grisogono founder Fawaz Gruosi said the necklace was part of the company's 20th anniversary collection, which was paraded at the Hotel Du Cap-Eden-Roc in Antibes outside Cannes.
Gruosi said 80 bodyguards, police, hotel security, and De Grisogono staff were on duty, but the necklace was missing when a check was made at the end of the night.
Another Swiss jeweller, Chopard, had gems worth $US1.4 million stolen from a wall safe in a room at the Suite Novotel hotel on the night of 16 May.
The entire safe was removed from the wall..