Residents of Catalan house where explosion killed one were preparing explosives - police source

MADRID (Reuters) - Residents of a house in Catalonia, where an explosion linked to Thursday's Barcelona van attack killed one person, were preparing explosives using gas cylinders, a Catalan police source said. Police said earlier that the explosion, about 100 km (62 miles) southwest of Barcelona in the town of Alcanar, was related to the van attack, which so far has left 13 people dead. (Reporting by Carlos Ruano; Writing by Angus Berwick; Editing by Julien Toyer)