(S (S (S (BASENP (NNS Investigators)) (VP (VBP say) (SBAR (S (BASENP (PRP they)) (VP (VP (VBP are) (ADVP (RB currently))) (ADJP (JJ unsure) (SBAR (SBAR (IN if) (S (BASENP (DT the) (NN blast)) (VP (VBD was) (ADJP (RB purely) (JJ accidental))))) (CONJP (COMMA ,) (CC or)) (SBAR (IN if) (S (BASENP (NN foul) (NN play)) (VP (VBD was) (VP (VBN involved)))))))))))) (COMMA ,) (SBAR (IN as) (S (BASENP (DT all) (NNS efforts)) (VP (VBD were) (VP (ADVP (RB initially)) (VP (VBN focused) (PP (IN on) (S (VP (VBG attempting) (S (VP (TO to) (VP (VB locate) (BASENP (NNS survivors)))))))))))))) (PERIOD .))