De Grisogono announced that the necklace was stolen from the Hotel Eden-Roc in the resort town of Antibes, in the south of France.
“A necklace was stolen during the Cannes film festival and we are working with authorities,” a spokesman for the jeweller said, refusing to comment on the circumstances of the theft or the exact value of the necklace.
Police confirmed they were investigating a complaint filed by the Swiss jeweller and that a necklace had gone missing in Antibes, near Cannes.
France Info radio reported that the missing necklace was worth 1.9 million euros and had been stolen during a gala evening Tuesday at the chic Eden Roc hotel attended by, among others, Paris Hilton and Sharon Stone.
It is second high value theft to hit the Cannes festival in a matter of days.
On Friday thieves stole Chopard jewellery worth around 1.4 million francs from a safe in a room at the Novotel hotel.
In a scenario itself worthy of a movie, thieves entered the hotel room of an American woman employee of Chopard and ripped out the strongbox in the wardrobe, according to police reports.
A Chinese film producer blasted France for its “really bad” level of public safety after he was the victim of a burglary at this year's festival.
Zhang Qiang expressed his outrage on his blog just days after the apartment he was renting in the resort was targeted by thieves.
The vice president of the powerful state conglomerate China Film Company discovered the apartment he had hired out for the festival had been targeted when he returned home from dinner last Thursday.