Suspects in Spain's twin terror attacks were preparing an even bigger assault but were thwarted in their plans and forced to act quickly, police said Friday.

"They were preparing one or several attacks in Barcelona and an explosion in Alcanar stopped this as they no longer had the material they needed to commit attacks of an even bigger scope," said Josep Lluis Trapero of Catalonia's police.

He was referring to a blast in a house in the town of Alcanar on Wednesday evening which police said caused one death and was caused by an attempt to make explosive devices.