A 23-year-old man from the eastern French city of Strasbourg has been identified as the third armed man involved in the attack on Paris' Bataclan music hall, police sources say.
Foued Mohamed Aggad had travelled to Syria with his brother and a group of friends at the end of 2013, a source close to the investigation said on Wednesday.
In an interview with BFM TV in Paris on Wednesday, Manuel Valls, France's prime minister, confirmed the report, as he pledged that France would carry out more arrests.
"What is important is that the investigation is progressing, that the accomplices are found out, that arrests happen," he said.
In Photo: Tears and mourning in France
Aggad was reportedly identified using DNA samples provided by his mother.
The two other attackers involved in the massacre of 90 concert-goers at the Bataclan - Omar Ismail Mostefai, 29, and 28-year-old former Paris bus driver Samy Amimour - had also been in Syria.
According to French news reports, Aggad was one of the two attackers, who blew themselves up with suicide belts packed with explosives after the killing spree, the worst of the November 13 Paris attacks.
The third was shot by police who stormed the venue with hundreds of people still inside.
Most of the group of six men from Strasbourg who went to Syria with Aggad were arrested in the Meinau area of the city on their return in May last year and are all in custody on terrorism charges.
But Aggad stayed on in Syria, the source said.
Al Jazeera's Jacky Rowland, reporting from Paris, said the identification of Aggad was significant as it allows police to establish the identities of other suspects.
"The more identities that they can find, the more that the police can start to draw a broader net to try to establish the connection," she said.
But in terms of catching the other suspects, that might take some time, our correspondent said.
At least one suspect, Salah Abdelsalam, has reportedly fled back to Syria.
Others 'killed fighting'
Investigators believe two brothers from the group of attackers, Mourad and Yassine Boudjellal, were killed fighting with the Islamic State of Iraq and the Levant (ISIL) group.
When questioned on their return, the men claimed that they had been horrified by what they had witnessed in Syria and had started to dribble back to France from February 2014.
They claimed to have gone to Syria for humanitarian work but prosecutors believe they were part of ISIL, which claimed responsibility for the carnage in Paris.
Police suspect the Strasbourg group had been recruited by Mourad Fares, 31, who was known to French intelligence for recruiting fighters through social media and the internet.
Fares - who Bernard Cazeneuve, France's interior minister, has described as a "particularly dangerous individual" - was arrested in August 2014 in Turkey before being handed over to the French authorities.
Cazeneuve said he was an important link between various "jihadist terrorist movements", including ISIL and al-Qaeda's Syrian affiliate al-Nusra Front.
Nearly 1,500 people were watching the Californian band Eagles of Death Metal perform at the Bataclan when the attackers burst in last month, leaving 90 dead and hundreds hurt, most of whom were aged under 40.
Source: Al Jazeera and agencies