ity ▁as ▁an ▁exhib it ▁is ▁disput ed . ▁ ▁Pres ence ▁of ▁the ▁bomb ▁on ▁the ▁train ▁On ▁the ▁morning ▁of ▁the ▁bomb ings , ▁the ▁trains ▁were ▁double - checked ▁by ▁the ▁E OD ▁police ▁to ▁be ▁sure ▁that ▁no ▁un expl oded ▁devices ▁were ▁present . ▁The ▁th ir teenth ▁bomb ▁was ▁not ▁found ▁at ▁this ▁time . ▁The ▁only ▁E OD ▁polic eman ▁who ▁remembered ▁handling ▁a ▁heavy ▁bag ▁( the ▁th ir teenth ▁bomb ▁we ighed ▁around ▁ 1 1 ▁kil og rams ▁( 2 4 ▁l bs )) ▁that ▁morning ▁in ▁El ▁Poz o ▁station ▁assert ed ▁posit ively ▁that ▁the ▁heavy ▁bag ▁he ▁handled ▁in ▁the ▁train ▁station ▁did ▁not ▁contain ▁the ▁bomb . ▁ ▁Correct ▁handling ▁of ▁the ▁evidence ▁A ▁Spanish ▁police ▁report ▁concluded ▁that ▁the ▁bomb ▁could ▁have ▁been ▁manip ulated ▁by ▁un ident ified ▁persons ▁in ▁If ema ▁( in ▁Spanish , ▁" p udo ▁ser ▁manip ul ada ▁por ▁personas ▁no ▁identific adas ▁en ▁el ▁If ema "), ▁which ▁was ▁the ▁Madrid ▁exhibition ▁center ▁where ▁objects ▁found ▁in ▁the ▁trains ▁were ▁tempor arily ▁stored . ▁While ▁DNA ▁from ▁an ▁un ident ified ▁male ▁was ▁found ▁on ▁or ▁in ▁the ▁bag , ▁Spanish ▁police ▁assert ed ▁that ▁the ▁' chain ▁of ▁cust ody ' ▁was ▁un bro ken ▁and ▁the ▁P P ▁leader , ▁Mar iano ▁R ajo y , ▁assert ed ▁in ▁March ▁ 2 0 0 6 ▁that ▁he ▁had ▁no ▁doub ts ▁about ▁the ▁valid ity ▁of ▁this ▁police ▁exhib