The Toulouse gunman’s brother has been taken to Paris for further questioning by intelligence officers.
Abdelkader Merah was arrested on Tuesday as police sought help in trying to convince 23-year-old Mohammed to surrender.
AFP quoted judicial sources on Saturday as saying Abdelkader was “proud” of his brother’s slayings.
He still denies having any prior knowledge of them, although police say he was present at the theft of Mohammed’s getway vehicle, a Yamaha scooter.
Officers later found explosives in a car that he owned.
They also said Abdelkader has links to radical Islamists.
Investigators are now trying to establish whether the gunman had logistical or ideological support, or was a true lone wolf.