Investigators believe that a second militant who played a direct role in last week’s assault on this storied city could still be at large, a U.S. law enforcement official said Tuesday, as authorities in France and Belgium scrambled to identify the potential assailant.

Seven militants blew themselves up or were killed by police during Friday’s deadly attacks, three of them around a sports stadium, three inside a concert hall and one outside a cafe.

An international manhunt is underway for an eighth suspect, Salah Abdeslam, who is believed to have played an important role in the attacks. One of his brothers, Brahim, has been named as the militant who blew himself up on the cafe’s terrace.

Some witnesses placed the two brothers in a car used to open fire on a string of Paris eateries, said the U.S. official, who was briefed on the ongoing investigation but was not authorized to speak publicly about it. Others said there were three men inside the vehicle, not two.

“They didn’t see a lot,” the official said, “except some insisted there was a third person in the car.”

Investigators do not have a name or facial description for the potential suspect, the official added.

France says Islamic State conceived the bombing-and-shooting rampage in Paris, which killed at least 129 people who were enjoying a night out in cafes and restaurants and at a rock concert and a soccer match.

French President Francois Hollande has declared that his country is “at war” with the extremist group and has asked lawmakers to give the government broader powers to counter imminent threats to national security.

French warplanes pounded Islamic State targets in Syria late Tuesday, the third straight night of airstrikes against the group. French Defense Minister Jean-Yves Le Drian told TF1 TV that 10 fighter jets were taking part in the bombardments. He said the number would increase to 36 when a French aircraft carrier reaches the area.

There were also more raids Tuesday on locations across France that are suspected of links to extremist activity, though not necessarily tied directly to the attacks on Paris.

Interior Minister Bernard Cazeneuve told French radio that 128 locations were targeted overnight Monday, on top of 168 raids the night before. He said the government was mobilizing 115,000 police officers, gendarmes and soldiers to protect the public.

Officials in France and Belgium, where many of the Paris attackers either lived in or had connections to a Brussels neighborhood known to harbor radical Islamists, are said to be focusing their attention on a Belgian national named Abdelhamid Abaaoud as the potential ringleader.

He is believed to be in Syria, but is not thought to be the militant heard in an audio recording taking credit for the attacks on behalf of Islamic State, according to the U.S. law enforcement source. An analysis of the recording points to Fabien Clain, a Frenchman has been linked to previous plots dating back to 2012 and is also thought to be in Syria.

“It’s him,” the U.S. official said.

Investigators believe that at least some of the Paris attackers posed as Belgian businessmen when they entered France in the days before Friday’s rampage, the official said. A cell phone thought to have been used by the militants has been recovered, the official added.

On Tuesday, the Belgian federal prosecutor’s office charged two men arrested over the weekend, Mohammed Amri and Hamza Attou, with being part of the plot.

Lawyers for the two suspects acknowledge that their clients drove to Paris to pick up the fugitive Abdeslam and bring him to Brussels early Saturday. But they say the men deny any role in the attacks.

Amri’s lawyer, Xavier Carrette, said Abdeslam called his client Friday night asking for the ride, but made no mention of the attacks, the Belgian broadcaster RTBF reported. Attou went to keep Amri company, according to his attorney, Carine Couquelet.

Belgian media reported that ammonium nitrate, an ingredient often found in homemade explosives, was found at the men’s residences. But prosecutors said tests were still being conducted to determine the nature of the materials seized and cautioned against drawing any hasty conclusions.

The developments in the fast-moving investigation came as Russian security officials confirmed for the first time that a bomb brought down a Russian commercial airliner over Egypt last month, killing all 224 people on board.

Islamic State has claimed responsibility for that attack as well as for the assault on Paris, sparking increasing alarm over the group’s apparent growing ambition, sophistication and reach in its terror campaign.

On Tuesday, a soccer game between Germany and the Netherlands was abruptly canceled because of a bomb threat. Police said they had “concrete evidence” that someone wanted to set off an explosive device at the stadium in Hanover. Another bomb threat about an hour earlier proved to be a false alarm, they said.

U.S. Secretary of State John F. Kerry, visiting Paris in a show of solidarity with France, met with Hollande on Tuesday to discuss how to increase the pressure on Islamic State. Hollande will travel to Washington next week to hold talks with President Barack Obama.