More than a dozen armed men stole millions of dollars worth of jewels from two high-security trucks on a motorway south of Paris overnight, a French police official said on Wednesday.
The robbers held up the trucks at a toll payment station in the Yonne area and drove off in four cars.
Local media said the jewels were worth $9.5m and that the gang used gas to force security transport personnel out of their vehicles.
Nobody was injured in the attack and the trucks had been found burnt out, the police official said.
France has seen repeated jewellery thefts. In November, two gunmen robbed a Cartier jewellery boutique in a tourist-filled Paris neighbourhood, fled a police chase across the Seine River, took a hostage and then surrendered.
Last month, eight people were convicted in connection with a spectacular 2008 jewel theft at a Harry Winston boutique in Paris, when three cross-dressing gunmen stole about $92m in goods.
In 2013, southeast France was hit with a spate of jewellery thefts, including two in Cannes during the city's famed film festival. In one, a gunman walked into a jewel show at the Carlton International Hotel, stole
$136m in loot, and disappeared down a side street in one of the most lucrative jewellery heists ever.