France has confirmed that a second Frenchman features in a videoshowing the beheading of Syrian prisoners, and the body of US hostage killed by Islamic State (IS).
French media quote unnamed official sources as saying he is a 22-year-old from an eastern suburb of Paris.
Earlier, the government named Maxime Hauchard, from Normandy, as a militant in the video released at the weekend.
About 1,000 French jihadists are thought to have gone to Syria and Iraq.
On a visit to the Australian capital Canberra, French President Francois Hollande on Wednesday told reporters that "there were two French people" in the latest video of IS militants.
"One has been categorically identified and the other one is in the process of being identified," he said.
The AFP news agency quotes a source close to the investigation as saying that the second man is known as Abu Othman, a 22-year-old from a Parisian suburb.
In the latest IS video - unlike previous ones showing beheadings - several militants appears with their heads uncovered.
Earlier this week, a French prosecutor named Mr Hauchard as one of those leading Syrian prisoners to their execution.
The video also shows the severed head of Abdul-Rahman Kassig, a US aid worker who was kidnapped in Syria last year.
Concerns about the involvement of French citizens in the conflict were heightened after a gun attack earlier this year on a Jewish museum in Brussels.
The attack, which killed four people, was carried out by 29-year-old Mehdi Nemmouche, a Frenchman who had fought as a jihadist in Syria.