Mohamed Houli Chemlal is one of four surviving suspects who gave evidence.
He and Driss Oukabir have both been charged with membership of a terrorist organisation and murder.
Salah al-Karib has been detained pending further investigations, while Mohammed Aallaa was released on bail.
According to Houli Chemlal, the group's plans - which he had known of "for at least two months - were scaled back when a house packed with bomb-making equipment blew up the day before.
He was injured in the accidental blast that reduced the house to rubble in the town of Alcanar.
