Spanish police say they now believe that 12 people were behind the Barcelona attacks.
One man is still on the run.
Spanish and French border security has been beefed up in the search for Younes Abouyaaqoub.
Authorities believe the 22-year-old Morrocan was the driver of the van at Las Ramblas that killed 13 people and injured hundreds.
There are fears that he may have slipped over the border into France.
The self-styled Islamic State has claimed responsibility for the attacks.
Catalan Police Chief Major Josep Trapero said: “At this point, without discarding other possibilities, Abouyaaqoub is the person who perpetrated the attack over 200 metres that killed and wounded so many people.”
Cell had more than 100 gas cannisters
Investigators have found the remains of two people in the house that exploded in the nearby the town of Alcanar.
More than 100 butane gas cylinders were found at the house, and also, according to Spanish media, traces of TATP, or triacetone triperoxide, a highly volatile explosive.
It’s believed the gas canisters were to be used in a massive attack.
When that failed, they improvised with a Plan B at Cambrils, where five suspects were shot dead.
Four people have been arrested so far in connection with the attacks.