Cannes (CNN) -- The value of jewels stolen from an exhibition in the French resort city of Cannes on Sunday is close to $136 million -- more than twice the amount stated in earlier reports -- the Nice prosecutor's office told CNN Monday.
The robbery -- the third such heist around the city since May -- happened Sunday morning at a jewelry exhibition at the Carlton Hotel, according to Philippe Vique, deputy prosecutor for organized crime in the prosecutor's office.
Earlier, a Nice police official told CNN on condition of anonymity that the jewels were worth about $53 million.
The robber, whose face was covered by a hat and a scarf, had a semiautomatic pistol and threatened to shoot the exhibitors and guests, Vique said.
Security guards were present but unarmed, he said. No one was injured.
The gems were supposed to have been on display until the end of August.
The robbery follows two major jewel heists this year at events tied to the Cannes Film Festival.
During the festival in May, a necklace worth $2.6 million was stolen from a hotel party shortly after jewels worth more than $1 million were stolen from a safe in a hotel room.
Jeweler de Grisogono said the necklace was part of a collection making its debut.
The jewels stolen in May were from the Swiss firm Chopard, which was sponsoring the festival.
CNN's Stephanie Halasz, Vladimir Duthiers and Lauren Russell contributed to this report.