The French news media reported that the thieves who commandeered the Mercedes eventually released the driver, an official and a bodyguard on the side of the road. The police initially said the thieves wielded Kalashnikov rifles, but later said they had handguns. The Mercedes was later found abandoned and burned, the police said, its charred remains discovered near a wooded area, along with one of the gang’s burned BMWs.

Prosecutors are investigating whether the robbery was an inside job, as the gunmen appeared to know the convoy’s route. The French police have opened an investigation into “armed theft by an organized gang,” but there have been no arrests.

“The robbers were experienced, well organized,” said Nicolas Comte, a police officer and secretary general of Unité SGP Force Ouvrière, a leading police union. “They did it with self-control and equipment, without committing any mistake. We can imagine that they knew that a large amount of money was being carried, and that perhaps people in the convoy knew some of the robbers.”

The police did not reveal the names of the victims. In a statement published on the S.P.A., the state news agency of Saudi Arabia, the Saudi Embassy in Paris said that the stolen car was a Mercedes Viano with German plates and rented by a Saudi citizen, “who was heading for the airport with his luggage.”

“On the way, the driver was forced to get out the car,” the statement said. “The luggage and car were stolen.”

On the official Facebook page of the Saudi Ministry of Foreign Affairs, a statement was also issued denying reports by the French police and news media that a car belonging to the Saudi Embassy had been attacked on the way to the airport, “where money and sensitive documents were stolen.” Such reports, the statement said, “are not true at all.” The statement also quoted one delivered by the embassy saying that it was cooperating with the French authorities.

The crime fit the pattern of other recent attacks in the French capital, law enforcement officials said, and Mr. Comte, the police officer, said the threat of violence and the element of surprise suggested that its perpetrators could be from Eastern Europe or the Balkans. In recent years, criminals from the former Yugoslavia, including globe-hopping jewel thieves known as the Pink Panthers, have snatched jewels worth hundreds of millions of dollars, from Dubai to Geneva to Paris, in swift “snatch and grab” attacks that usually take no more than three minutes.