▁crash ing ▁down ▁on ▁about ▁ 2 0 0 ▁din ers ▁and ▁employees , ▁killing ▁ 1 8 ▁people ▁and ▁inj uring ▁ 8 2 ▁others , ▁including ▁fifteen ▁Americans ▁working ▁at ▁the ▁nearby ▁Torre j ón ▁Air ▁Base ▁who ▁frequ ented ▁the ▁restaurant . ▁At ▁the ▁time ▁it ▁was ▁the ▁worst ▁attack ▁in ▁Spain ▁since ▁the ▁Spanish ▁Civil ▁War . ▁ ▁Bomb ing ▁At ▁about ▁ 2 2 : 3 0 , ▁a ▁bomb ▁expl oded ▁in ▁the ▁El ▁Des c ans o - La ▁Casa ▁de ▁las ▁Cost illas ▁restaurant , ▁causing ▁the ▁three - story ▁building ▁housing ▁the ▁restaurant ▁to ▁collapse . ▁The ▁building ▁crash ed ▁down ▁on ▁about ▁ 2 0 0 ▁din ers ▁and ▁employees ▁present ▁in ▁the ▁restaurant , ▁killing ▁ 1 8 ▁people ▁and ▁inj uring ▁ 8 2 . ▁Fif teen ▁American ▁serv ic emen ▁of ▁the ▁nearby ▁American ▁Torre j ón ▁Air ▁Base ▁were ▁among ▁the ▁injured , ▁but ▁while ▁being ▁frequ ented ▁by ▁air ▁base ▁staff ▁the ▁timing ▁of ▁the ▁bomb ▁occurred ▁at ▁an ▁hour ▁few ▁Americans ▁typically ▁were ▁present . ▁The ▁police ▁investigation ▁concluded ▁that ▁the ▁explos ion ▁was ▁caused ▁by ▁a ▁ 1 3 - p ound ▁ch lor at ite ▁bomb ▁plant ed ▁near ▁the ▁bath room ▁of ▁the ▁restaurant , ▁consisting ▁of ▁a ▁chemical ▁comp ound ▁made ▁up ▁of ▁pot ass ium , ▁sul fur ▁and ▁ch lor ate , ▁a ▁type ▁of ▁explos ive ▁said ▁to ▁be ▁rarely ▁used ▁by ▁domestic ▁Spanish ▁terror ist ▁groups . ▁ ▁Investig