The older brother of Salah Abdeslam -- the man being hunted internationally for his alleged role in the Paris terror attacks last week -- urged the suspect Tuesday to turn himself over to authorities.
"I would tell him to surrender. That's the best solution," Mohamed Abdeslam told CNN's Erin Burnett. "But of course, if he has something to do with it, he must accept responsibility."
Another Abdeslam brother, Ibrahim, reportedly blew himself up outside a cafe during a series of coordinated attacks throughout the city Friday night that killed at least 129 people and wounded hundreds more.
Authorities say six of the terrorists either killed themselves or were killed by police in the harrowing attacks that lasted hours.
"These are not regular people," Mohamed Abdeslam, 29, said of his brothers. "You cannot have the slightest doubt that they have been prepared, that they must not leave any trace which would cause suspicion that they might do such things. And even if you saw them every day, their behavior was quite normal."
Police stopped Salah Abdeslam, 26, hours after the attacks, in a car on his way toward the Belgian border but let him go because he apparently hadn't yet been linked to the terrorist operation.
Suspects questioned by Belgian authorities in February
Both he and Ibrahim, 31, were previously known to authorities: Belgian prosecutor Eric Van Der Sypt told CNN's Ivan Watson that police questioned the Abdeslam brothers in February.
"Ibrahim tried to go to Syria and was sent back by the Turks in the beginning of 2015," Van Der Sypt said. "It was after that that we questioned him."
Both brothers were released, the federal prosecutor said, after they denied wanting to go to Syria.
He said Belgian authorities were also trying to keep an eye on Bilal Hadfi, one of the suicide bombers who struck outside the Stade de France, according to several sources. "We knew (Hadfi) was in Syria," Van Der Sypt said. "But what we didn't know is apparently he was back, as he blew himself up in Paris. But we had no knowledge of the fact that he was back in Europe."
None of the individuals identified so far in the Paris attacks has been on any U.S. watch lists, multiple U.S. officials told CNN, raising questions about how effectively the U.S. and its allies are able to track foreign fighters traveling to Syria and Iraq.
'At war' and launching airstrikes
Declaring the country is "at war," French President Francois Hollande has proposed extending the state of emergency for a further three months, along with sweeping new anti-terrorism laws.
Security forces conducted more than 128 new raids around the country overnight, Interior Minister Bernard Cazeneuve said Tuesday during a radio interview.
Meanwhile, outside the country, French warplanes have launched wave after wave of airstrikes in recent days on ISIS' de facto capital of Raqqa in northern Syria, and a major Belgian police operation was conducted Monday in the Abdeslams' home base in Molenbeek, a Brussels suburb with a history of links to Islamist terror plots.
Belgian authorities say two men detained over the weekend in Molenbeek in connection with the attacks are now under arrest for "attempted terrorism and participation in the activities of a terrorist group." Their identities haven't been disclosed.
Tracking the suspected mastermind
Before the Paris attacks, France and its allies had tried to target a prominent ISIS member who is believed to have planned the assault on the French capital, a French source close to the investigation said.
Western intelligence agencies had attempted to track Abdelhamid Abaaoud, a Belgian citizen thought to be in Syria, but they weren't able to locate him, the source told CNN on Tuesday.
Abaaoud had been implicated in the planning of a number of terrorist attacks and conspiracies in Western Europe before the Paris attacks.
Believed to be close to ISIS leader Abu Bakr al-Baghdadi, he was linked to a plan to attack Belgian police that was thwarted in January. He has since been featured in ISIS' online English-language magazine. His current whereabouts are unknown.
One of the voices heard in a video put out by ISIS claiming responsibility is that of Fabien Clain, a senior French ISIS operative, a French security source briefed on the investigation told CNN.