▁van ▁found ▁near ▁Al cal á ▁de ▁Hen ares ▁station ▁on ▁the ▁day ▁of ▁the ▁bomb ings , ▁and ▁the ▁device ▁that ▁was ▁left ▁by ▁the ▁high ▁speed ▁railway ▁line ▁connecting ▁Madrid ▁and ▁Se ville . ▁ ▁The ▁only ▁explos ive ▁posit ively ▁identified ▁in ▁any ▁site ▁connected ▁to ▁the ▁bomb ings ▁has ▁been ▁G oma ▁ 2 ▁E CO ▁and ▁the ▁sentence ▁in ▁the ▁trial ▁concluded ▁that ▁it ▁was ▁likely ▁that ▁the ▁bomb s ▁contained ▁this ▁explos ive ▁or ▁a ▁mixture ▁of ▁it ▁with ▁its ▁prede cess or ▁product ▁G oma ▁ 2 ▁EC . ▁ ▁Pot ential ▁prevent ion ▁of ▁the ▁bomb ings ▁ ▁Some ▁of ▁the ▁alleg ed ▁Islam ist ▁perpet rat ors ▁had ▁reported ly ▁been ▁under ▁surve ill ance ▁by ▁the ▁Spanish ▁police ▁since ▁January ▁ 2 0 0 3 . ▁According ▁to ▁the ▁Spanish ▁newspaper ▁El ▁Mundo , ▁ 2 4 ▁of ▁the ▁ 2 9 ▁alleg ed ▁perpet rat ors ▁were ▁inform ers ▁and / or ▁controlled ▁by ▁the ▁C uer po ▁Nacional ▁de ▁Pol ic ía , ▁Civil ▁Guard ▁and ▁Centro ▁Nacional ▁de ▁Intel igen cia ▁(" National ▁Centre ▁for ▁Int elligence ") ▁from ▁the ▁time ▁before ▁the ▁attacks .< ref > {{ cite ▁web ▁| url = http :// www . exp atica . com / actual / article . asp ? sub channel _ id = 8 2 & story _ id = 3 7 2 3 1 ▁| title =' ' Mad rid ▁bomb ing ▁accused ▁' under ▁watch ▁since ▁ 2