On Friday, Josep Lluis Trapero, the police chief in Spain's northeastern region of Catalonia, said he could not confirm that the van driver was one of the five men shot dead by the police after a second attack in Cambrils.
Seventeen-year-old Moussa Oukabir, initially reported to be the driver of the van, was among the five killed.
So far, the Spanish police have arrested four people who have no previous links to terrorism.
Police said three of the arrested men are Moroccan and one is Spanish. They are aged 21, 27, 28, and 34.
Police forces are also hunting for three men in connection with the attack, one of whom has been identified as Younes Abouyaaqoub, 22, who is thought to be the van driver.
On Thursday, a van rammed into a multitude of people on Rambla avenue in the center of Barcelona, killing at least 13 and injuring some 100 others. The driver fled the scene after the attack.
The vehicle travelled several hundred meters, running over pedestrians and cyclists on its way, before stopping at a decorative mosaic near a subway station.
The Daesh Takfiri group has claimed responsibility for the attack.
In the early hours of Friday morning, in the town of Cambrils, 100 kilometers away from Barcelona, five “alleged terrorists” drove into pedestrians before being shot dead by security forces.
One of the pedestrians died and six others sustained injuries in the second attack.
The five assailants, who were wearing explosive vests, were then shot dead, police said. The bomb vests were detonated by the force’s bomb squad. Police say one of the five could have been the missing driver of the Barcelona van.
Police said the two attacks were linked and they affected people of at least 34 different nationalities, including the UK, France, Venezuela, Australia, Ireland, Peru, Algeria and China.
Officers believe that the two attacks are related to an explosion in the early hours of Thursday at a house in Alcanar, 130 km south of Barcelona. Police sources said the house was being used as a lab to make weapons with explosive gas.
At least one person died and more than 16 were injured in the blast.
The Barcelona incident was the deadliest attack in Spain since March 2004, when Takfiri militants bombed commuter trains in Madrid, killing over 190 people and wounding more than 1,800.