Complicating the manhunt, though, was the fact that police have so far been unable to officially identify who exactly is at large.
Those four suspected members of the cell were in court less than 24 hours after police killed Younes Abouyaaqoub, the suspected driver of the van in Barcelona.
Today it emerged police are focusing on the theory that Younes Abouyaaqoub, the driver of the van that mowed down and killed 14 people on Barcelona's Las Ramblas before stabbing Spaniard Pau Perez to death and stealing his auto, spent his time on the run sleeping by day and walking at night to minimise his chances of being detected by CCTV cameras or noticed by members of the public.
Moroccan, 18-years-old, one of the men killed in Cambrils.
"We are working in that line", Trapero said. Here's what we know...
Investigators say he allegedly drove the van into a crowd in Barcelona's busy La Rambla area on Thursday and fled on foot.
Police believe the cell members had planned to fill the vans with explosives and create a massive attack in the Catalan capital.
The house in Catalonia, a city where police continue to hunt for Abouyaaqoub, was discovered to have stored more than 100 butane gas tanks, and other ingredients meant for explosives.
Until Thursday, just hours before the Barcelona attack, numerous young men seemed to be living completely normal lives. Police say Es Satty died in Wednesday's explosion, apparently while he was building a bomb. Trapero confirmed the imam was part of the investigation but said police had no solid evidence that he was responsible for radicalizing the young men in the cell.
Photos show the living situation of Es Satty.
His former mosque denounced the deadly attacks and weeping relatives marched into a Ripoll square on Saturday, tearfully denying any knowledge of the radical plans of their sons and brothers.
He is also suspected of having stabbed to death 34-year-old Pau Perez after hijacking his vehicle to make a getaway.
The imam Abdelbaki Es Satty has stayed in Belgium in 2016, in the municipality of Machelen, in the large suburb of Brussels, "between January and march 2016", said to AFP the mayor of the adjacent commune of Vilvoorde, Hans Bonte, who oversees the municipal police in the two communes.
"We have to talk to European police to notify them of the identity because this person... is likely being sought in all European countries", Forn said, Agence France-Presse reported.
Essati, who was in his 40s and who is reported to have had links to Islamic extremists going back at least a decade, somehow brought the young men under his influence after establishing himself as an imam in their mountain town of Ripoll, even though few of the young men had a history of regularly attending mosque. Police shot dead the five attackers, some of whom were wearing fake explosive belts and carrying knives. They were normal boys. They didn't steal. Never had a problem with me or anybody else.
Some people have made her son "crazy" to do something this bad, she said, adding that her son told her he was going to Germany for holidays, and did not appear acting differently in the past months. "His last message to me was that he was lying on the beach with friends". "Outside, I don't know". Rented or hijacked vehicles have formed the backbone of a strategy to attack the West and its cultural symbols. But in the last two years, the extremist group has steadily lost ground in its self-declared caliphate in Iraq and Syria.
TWO massacres left 14 people dead and more than 100 injured in Spain.
It was first claimed that Moussa Oukabir was driving.
Fiona Wilson, his daughter, described her father as an adventurous traveler and thanked those who helped him and her mother in his final moments.
In this watermarked frame grab from CCTV released by the Spanish newspaper El Pais on Monday Aug. 21, 2017, a suspect. believed to be Younes Abouyaaqoub is is captured by a security camera walking through La Boqueria market seconds after a van crashed into pedestrians in Barcelona last August 17.
"We are a broken family", niece Raquel Baron Lopez posted on Twitter.
By late Saturday, the Catalan emergency service said 53 attack victims were still hospitalized, 13 of them in critical condition.