Several Kalashnikovs have been found in an abandoned car believed to have been used by some of the Paris attackers, French judicial sources say.
The black Seat car was found in the eastern Paris suburb of Montreuil on Sunday, suggesting some of the attackers got away.
Earlier, the first of the seven dead attackers was named as Ismail Mostefai. Six people close to him are in custody.
France is in three days of mourning for the 129 people killed in the attacks.
Prime Minister Manuel Valls most of the bodies had been identified and said the process should be completed in the coming hours.
A special service for the victims, including 350 people wounded, and the survivors will be held at Paris's Notre Dame Cathedral later on Sunday.
Friday's attacks, claimed by Islamic State (IS) militants, hit a concert hall, a major sports stadium, restaurants and bars in the French capital.
In political developments:
- Mr Valls says France will continue with air strikes against IS in Syria, and described the group as a very well-organised enemy
- EU justice and interior ministers will hold an emergency meeting on Friday to discuss security measures
- President Francois Hollande cancelled plans to attend a G20 meeting in Turkey on Sunday and has held meetings with political leaders
The Seat car found in Montreuil is believed to have been used by gunmen who opened fire on people in restaurants on Friday, police say.
Several AK47 rifles were found in the car, French media quotes judicial sources as saying.
It appears to confirm the theory that some of the gunmen managed to flee after the attacks, the BBC's Hugh Schofield reports from Paris.
These men may then have driven north in another car to Belgium, he adds.
Five men were arrested in Belgium on Saturday - in the town of Molenbeek near Brussels - in connection with the Paris attacks, Molenbeek's mayor told Belgian TV.
At least one of those arrested was believed to have spent Friday in Paris, Belgian Prime Minister Charles Michel has said.
A Volkswagen Polo with Belgian number plates was found near the Bataclan concert venue, where nearly 90 people were killed. Paris chief prosecutor Francois Molins said that car had been rented by a French national living in Belgium.
"We can say at this stage of the investigation there were probably three co-ordinated teams of terrorists behind this barbaric act," Mr Molins said.
"We have to find out where they came from... and how they were financed."
A Syrian passport, found near the body of one of the attackers at the Stade de France, had been used to travel through the Greek island of Leros last month, Greek officials have confirmed.
Serbia says the holder of that passport had also crossed its border from Macedonia and sought asylum at one of its registration centres.
No direct link has yet been made with the holder of the passport and the attackers.
History of petty crime
Mostefai was reportedly identified after investigators found a severed finger at the scene of the worst atrocity, the Bataclan concert hall where more than 80 people died.
He came from the town of Courcouronnes, south of Paris and had lived in the city of Chartres 100km (60 miles) south-west of Paris until 2012 where he regularly attended a mosque.
Mostefai had a history of petty crime but was never jailed. The security services deemed him to have been radicalised in 2010 but he was never implicated in a counter-terrorism investigation.
Police are said to be trying to find out whether he travelled to Syria in 2014.
His father, brother and sister-in-law are among six people close to Mostefai who have reportedly been taken into police custody.
His brother said he had not had contact with him for several years following family disputes, but said he was surprised to hear he had been radicalised.
He was one of six children in the family and had travelled to Algeria with his family and young daughter, the brother said.
Friday night's attacks are the worst France has experienced in peacetime since World War Two. It is also the deadliest in Europe since the 2004 Madrid bombings.
Islamic State said it carried out the attacks on "carefully chosen targets" and were a response to France's involvement in the air strikes on IS militants in Syria and Iraq.
President Hollande said France had been "attacked in a cowardly shameful and violent way" and vowed to be "merciless" in its response to IS militants.