(S (S (S (BASENP (JJ Russian) (NNS newspapers)) (VP (ADVP (RB initially)) (VP (VBD suggested) (SBAR (S (BASENP (DT a) (NN bag)) (VP (VBD had) (VP (VBN exploded) (PP (IN on) (BASENP (DT the) (NN floor)))))))))) (COMMA ,) (SBAR (IN while) (S (BASENP (JJ local) (NN TV)) (VP (VBZ has) (VP (VBN shown) (NP (BASENP (NNP CCTV) (NN footage)) (PP (IN of) (BASENP (DT the) (NN explosion))))))))) (PERIOD .))