The incident in the coastal Catalonian town of Alcanar on Wednesday injured seven people and killed one. Late on Thursday, Catalan police sources told Reuters residents in the house were preparing gas explosives. Earlier media reports said first responders to the scene found at least 20 gas containers at the home, which is said to have housed squatters.
"What we contemplate is that this is a terrorist attack with the intention of killing the largest number of people," said Joseph Luis Trapero, chief of Catalan police, of Thursday's attack.
The van assault is being connected with the explosion, Trapero explained.
At least 100 people were injured in the van attack, and a Catalan government official disclosed that the death toll of 13 may yet rise. Two suspects being held in custody for questioning were not the drivers that mowed down civilians, a Spanish police official said. The driver remains at large.
One man was shot dead after running over police at a checkpoint after the attack, but he doesn't appear to be connected to the van ramming plot.
So far, Catalan police have confirmed they have no evidence or intelligence suggesting that a follow-up attack is imminent, but earlier it was revealed that the CIA reportedly warned Catalonia of a potential van ramming attack two months ago.