- 2 updates
A Cannes police source said authorities were investigating whether a second incident of vanishing jewels was a theft, a problem of inventory or a loss, a source said.
Another Swiss jeweller, Chopard, had gems worth $1.4 million stolen in the first week of the 12-day festival on the French Riviera.
Police said the Chopard jewellery had been in the safe at Suite Novotel hotel in central Cannes, which had been rented by an employee of the jeweller.
The entire safe was removed from the wall and taken during the night of 16 May.
Someone entered without forcing the door, a police source said.
A spokesman for Chopard, a sponsor of the Cannes festival, later played down the report, saying values had been exaggerated.
Jewellers and fashion houses use the world's largest film festival at Cannes as a promotional showcase, lending gowns and accessories to celebrities who are photographed.
The Cannes Film Festival was hit by a second suspected jewellery heist when a diamond necklace worth 2 million euros (£1.6 million) vanished during a star-studded party, according to upmarket jeweller De Grisogono.
Fawaz Gruosi, the founder of the Swiss firm, said the necklace was part of the company's 20th anniversary collection paraded by 20 models at the glitzy event at the Hotel Du Cap-Eden-Roc in Antibes outside Cannes on Tuesday night.
Sharon Stone and Paris Hilton were among the guests.
Mr Gruosi said 80 bodyguards, local police, hotel security, and De Grisogono staff had been on duty but when a check was made at the end of the night the diamond necklace was missing.
"We don't know exactly what happened ... it was one of the most beautiful items we had," Gruosi told said