Two men have been formally charged with murder over the deadly attacks in Barcelona and Cambrils whilst a third has been detained for further questioning and a fourth was freed on bail.
It comes after a court hearing where one of the group said the cell had been planning much larger attacks masterminded by a radical imam.
Mohamed Houli Chemlal, 21, admitted to his role in the plot and said they had hoped to target major destinations including Barcelona's Sagrada Familia church.
He was formally given preliminary charges for murder and membership of a terror organisation along with Driss Oukabir, 28, who hired the vans used in both of the attacks.
Chemlal was also charged with held fordealing with explosives.
A judge said that a third man, Sahl El Karib, can be held for another 72 hours for further questioning in the hearing at the National Court.
The final suspect, Mohamed Aalla, has been released on bail as the judge ruled the evidence against him was weak.
All four men are alleged to be the last surviving members of a 12-man terror cell behind the attacks which left 15 people dead and than 120 wounded.
Chemlal, 21, was found at the scene of a blast at a house in the town of Alcanar, in eastern Spain, which police say was being used as a bomb factory.
Imam Abdelbaki Es Satty, said to be the chief ideologist of the group, died in the explosion.
Chemlal said that Es Satty had been the chief planner of the attacks and had intended to blow himself up during a much larger rampage.
He gave his testimony from a wheelchair, after being taken to the court from hospital where he is being treated under guard, said court officials.
Police have previously said the house at Alcanar contained 120 gas canisters and explosive ingredients which they believe cell had planned to load onto vans and use in a series of coordinated attacks.
Chemlal was the only member of the four men to admit a role in a terror plot, court sources said.
The judge also heard from alleged accomplice Driss Oukabir, 28, whose brother was one of the five attackers shot dead in the resort of Cambrils last week.
Oukabir admitted hiring the vans used in last week's attacks, but said he thought they were going to be used in a house move, according to court sources.
He also reportedly admitted that the falsely told police that his identity documents - which were found in one of the vans - had been stolen. He said he told the lie out of fear.
The third suspect, El Karib, the owner of a cybercafe in Ripoll, claimed he was only making trying to make a profit when he bought at least two plane tickets for two alleged members of the cell.
He is being detained for another three days as investigations continues.
The final suspect, Aalla, was the registered owner of an Audi A3 used in last week's attack in Cambrils though he said in fact it was used by his sibling.
Police say one of Aalla's younger brothers died in Cambrils and another one is believed to be the second casualty in the Alcanar house blast where the imam died.
The judge ruled that the evidence against him was "not solid enough."
All four men were questioned in turn in the presence of court-provided lawyers, a spokeswoman for the prosecutors said.
National Court prosecutor Ana Noe had asked for all four to be sent to prison without bail on preliminary charges of being part of a terrorist organization, homicide, causing havoc and dealing with explosives.
It comes a day after the final alleged member of the cell to remain on the run, 22-year-old Younes Abouyaaqoub, was killed during a confrontation with police.