Police on Saturday night took into custody the father and brother of a French terrorist linked to a string of deadly Paris attacks and were searching their homes, a source close to the probe told AFP.
The body of the 29-year-old French national was found and identified at the Bataclan music hall, where 89 people were shot dead Friday when three gunmen wearing suicide vests opened fire on spectators, in the bloodiest of the attacks in Paris.
Investigators were also searching the homes of friends and relatives of the Frenchman, another source close to the enquiry told AFP.
The father's house is located in the small town of Romilly-sur-Seine, some 130 kilometers (80 miles) east of Paris, while his brother's is south of Paris in the Essonne region.
The brother, who is 34, contacted the police on his own initiative and was then taken into custody.
The Frenchman confirmed as one of the attackers was known to police as being close to radical Islam but had never been linked to a terrorism enquiry, Paris prosecutor Francois Molins said earlier Saturday.
Meanwhile in Belgium, police arrested several suspects in Brussels during raids connected to the Paris attacks, including one who was in the French capital at the time of the carnage, Prime Minister Charles Michel said.
Michel told Belgian television that the arrests were linked to "suspect vehicles" identified during the investigation by French police into the attacks that murdered at least 129 people and were claimed by Islamic State (ISIS).
The possible link to the new Paris attacks raises fresh fears that Belgium is becoming a hotbed of Islamist terrorism, coming just months after connections emerged to the Charlie Hebdo attacks and an attempted attack on an Amsterdam-Paris train in August.