Spanish police today said, a 12-strong terror cell that carried out two attacks in Spain this week had collected 120 gas canisters and was planning to use them in vehicle attacks. Catalan police chief Josep Lluis Trapero said the cell was still believed to consist of 12 men and had been planning attacks for more than six months. <br/><br/>One person remained at large, four were under arrest and there were two sets of human remains to be identified, he added. Trapero said police could not rule out that the suspect still at large had crossed the French border. Police are still hunting for the driver of the van that hit dozens of people on Barcelona's Las Ramblas, killing 13.<br/>