Antiterrorism police in France are questioning the brother of French gunman Mohamed Merah to determine if he played any part in the deadly shootings.
Merah admitted killing seven people in gun attacks before dying in a police siege.
His brother, Abdelkader Merah, was flown to Paris from Toulouse along with his partner and taken to the headquarters of the domestic intelligence agency (DCRI).
Reports say Abdelkader told police after the attacks he was "proud" of his brother. Merah's mother was released without charge on March 23.
Police are trying to find out if Mohamed Merah, a 23-year-old French citizen of Algerian descent, acted alone.
Merah, who described himself as an Al-Qaeda member, carried out three attacks, killing three soldiers before shooting dead three children and a teacher at a Jewish school.
Based on reporting by AFP and the BBC