A judge has charged two suspects allegedly linked to the attack in Barcelona with murder and freed another.
Mohamed Houli Chemlal and Driss Oukabir have also been charged with membership of a terror organisation and the possession of explosive and will be held in prison without bail.
Another suspect, Mohammed Aalla, has been released on bail due to weak evidence, while a fourth man, Salah el Karib, will be questioned by police for a further 72 hours.
Chemlal told Madrid's National Court on Tuesday (22 August) how there were plans for an even bigger attack with the targets some of the city's best known monuments such as the Sagrada Familia church.
The suspects who appeared in court are thought to be the only surviving members of a 12-man terror cell.
Oukabir was also questioned during the hearing during which he said he rented the van used in the Las Ramblas attack which killed 14 and left dozens injured, but thought it was going to be for a house move.
Chemlal has confessed to his participation in the Islamist cell behind the attack, but the other three say they are innocent.
Further details are emerging about Younes Abouyaaqoub, the 22-year-old Moroccan national who was the main suspect and who was shot dead in Subirats, 25 miles (40km) west of Barcelona on Monday (21 August).
One friend and neighbour described him as "A top notch guy. I know it's hard to believe this, especially after what happened. But he really was," El Pais reported.