Paris prosecutor François Molins speaking Saturday evening. | ALAIN JOCARD/AFP/Getty Images) Passport points to Syria, but officials urge caution An investigation is underway to determine whether the suspect entered Europe with migrants.

PARIS — Investigators are checking the authenticity of a Syrian passport found near the remains of a suicide bomber who blew himself up Friday in Paris, investigators told French media Sunday.

On Saturday, a Greek minister said that the passport matched the identity of a person who had traveled through the island of Leros on October 3 with a group of migrants from Syria. Serbian authorities added that the person had later passed through Serbia, before heading to Italy.

However, it remained unclear whether the attacker was the owner of the passport and investigators had yet to establish the passport's authenticity, police sources told Le Monde daily.

A reporter for newspaper Le Monde quoted French Justice Minister Christiane Taubira as saying the passport was a "fake." That could mean the man used a false document to enter Europe, or that it was planted on him as a false lead.

Greece Deputy Minister for Migration Yiannis Mouzalas also cautioned against linking the suspect to the flood of refugees.

Mouzalas told reporters Sunday that French authorities had only asked for information about one suspect called Ahmad Almohammad and born on September 10, 1990 in Syria. He traveled from Turkey to Leros, where he entered on October 3 by boat along with 198 people.

He was registered and fingerprinted by police in Leros in line with the usual process, Mouzalas said. He was then taken to the island of Rhodes, given a refugee certificate and the following day got a ticket to travel to Piraeus, before traveling on to Serbia and Croatia.

Mouzalas said Greek authorities had never received any information linking the passport holder to militant groups.

"This attack shouldn't be attributed to refugees. Most of them were people born and raised in Western countries. It's one thing to have better border control ... and another thing to erect fences and to make the refugee issue a tragedy for the refugees without resolving Europe's security issues," he was quoted as saying by the semi-official Athens news agency.

He added that there would be an "intensification of controls" and improvement to the hotspots registration centres.

The carefully organized nature of the attack broke a recent pattern of relatively unambitious, "lone-wolf" operations and led investigators to believe that the group had been backed up by accomplices in France and Belgium, some of whom may yet have to be apprehended.

Several witnesses at Paris' Bataclan concert hall, where the worst killing took place, described the attackers there as young men of Middle Eastern appearance who communicated in French and handled their weapons confidently.

While many details of the terrorists' identities and motivations remained unknown, an emerging picture underscored one of European authorities' worst fears — that militants affiliated to the ISIL terrorist group could have slipped into the vast crowds flooding into Europe to flee war and hardship in Syria.

Of the eight attackers, Molins said only two had been formally identified as of Saturday evening: one Frenchman who was known to security services; and the other was the man who was found with a Syrian passport near the scene of a suicide bombing near an entrance to the Stade de France stadium.

The Frenchman was later identified as Omar Ismail Mostefai, a 29-year-old Paris native of Algerian origin whose severed finger was found at the Bataclan.

Mostefai was said to have a series of convictions for petty crimes, but had not been to jail.

"I cannot be more precise for now," Molins said during a press conference in Paris, adding that he did not want to divulge further information that could disrupt ongoing raids to arrest suspects in Belgium. Police in Brussels raided the northern neighborhood of Molenbeek, which has a large Muslim population, arresting seven people.

Police in Paris found a rental car with Belgian plates that was allegedly used by the attackers parked near the Bataclan.

In several attacks over the past 18 months, including a shooting at a Jewish museum in Brussels, suspects have been linked to ISIL, either having fought with the group in Iraq and Syria or claiming allegiance to them and receiving instructions from afar.

Helen Popper in Athens contributed reporting to this article.

UPDATE: This story was updated to include new information about the authenticity of the Syrian passport found near one of the Paris terror attacks suspects.