PARIS — About 15 armed assailants ambushed two vans carrying millions of euros worth of jewels on a French highway in the middle of the night Wednesday, forcing out their drivers and speeding off into the Burgundy countryside, according to police. It was the latest in a string of big jewel heists in France.

French gendarmes and other authorities were combing the forests and towns in the region southeast of Paris for the attackers. No one was injured in the attack on the A6 highway connecting Paris and Lyon, and the drivers of the two vans were left at the scene unharmed, a police official said.

The perpetrators escaped in four cars and the two vans, which police later found burned and abandoned near the site of the attack, the official said.