Jewelry thieves have struck again at this year's Cannes Film Festival.

During a party at the Hotel Du Cap-Eden-Roc in the nearby resort town of Cap d'Antibes, France, thieves somehow made off with a $2.5 million diamond necklace despite the 80 security guards who were on hand for the party, according to CBC News.

The necklace and other jewels from Swiss gem firm De Grisogono were shown off by models at the party, which featured stars like Sharon Stone and Paris Hilton.

De Grisogono founder Fawaz Gruosi said that while accounting for the jewelry at the end of the party he realized that the pricey necklace was missing.

"We don't know exactly what happened," he tells Reuters. "It was one of the most beautiful items we had. The police are trying to figure out what happened."

"...It is actually the first time it has happened in our 20-year history," Gruosi added.

The theft came less than a week after $1.4 million worth of Chopard gems were stolen when thieves ripped a safe from the wall of the hotel suite of one of the company's employees in Cannes.

Both companies loan their jewels to the stars to wear on the red carpet and at parties, and the stars are usually accompanied by bodyguards to keep tabs on the expensive items.