According to El Pais newspaper, the bomb plan had failed due to explosions in Alcanar municipality Wednesday night.
Meanwhile, the Catalan police said Friday they were working on a hypothesis that terrorists were preparing the attacks in Barcelona and Cambrils for some time.
"We are working on the hypothesis that the terrorists were preparing the attacks in Cambrils and Barcelona for some time in Alcanar," Catalonia’s police force, the Mossos d'Esquadra, said in a tweet.
Earlier in the day it was reported that a fourth person was detained in relation to the attacks in Spain’s Barcelona and Cambrils, the Catalan police said. According to El Periodico newspaper, the fourth detention was carried out in Ripoll, also in Catalonia.
According to the police's statement, there are three Moroccan nationals and one Spanish national among the detainees. Non of them had a history of terrorism attacks.
"Four detentions – three in Ripoll and one in Alcanar. None of them had any type of terrorism-related past. Three of them are Moroccan and one is a Spaniard," Josep Lluis Trapero, chief of Catalonia’s police force, the Mossos d'Esquadra, said, as quoted by El Pais newspaper.
But the perpetrator of Barcelona van attack has not yet identified.
"The driver of the van has not been identified," Josep Lluis Trapero, chief of Catalonia’s police force, the Mossos d'Esquadra, said, as quoted by El Pais newspaper.
Several hours after the Barcelona tragedy, a van rammed into a crowd of passers-by in the coastal town of Cambrils 74 miles south of the Catalan capital, injuring seven people, including a police officer. A woman later died in hospital. In a following counter-terrorist operation, four attack suspects were killed and one died from wounds later.