Organizers of the Barcelona and Cambrils terrorist attacks, carried out on Thursday, had been planning to use gas canisters, Reuters reported quoting Catalan investigators.
Investigators believed a cell of at least eight people, possibly 12, may have been involved in the Barcelona and Cambrils operations.
The explosion was also in the town of Alcanar on Thursday. One person died and seven others were injured in that incident, police said. A man was also found dead in a car which had driven into a police checkpoint in Barcelona, though the police could not immediately confirm it was connected with the van attack.