BARCELONA, Spain (AP) — Catalan police say they are carrying out controlled explosions in the town where an extremist cell plotted the attacks in Barcelona and a seaside resort.

In a tweet Saturday, police urged residents of Alcanar not to be alarmed by the detonations in the town, where they believe the extremists rented a house used to prepare their attacks.

The house was destroyed by an apparently accidental explosion on Wednesday. Police believe the blast actually prevented a far more deadlier attack using explosives, forcing the extremists to use more “rudimentary” vehicles instead.