(S (S (NP (BASENP (DT The) (NN explosion)) (CC and) (BASENP (JJ subsequent) (NN fire))) (VP (VBD was) (VP (ADVP (RB originally)) (VP (VBN thought) (S (VP (TO to) (VP (VB have) (VP (VBN been) (BASENP (DT a) (JJ downed) (JJ commercial) (NN aircraft)))))))))) (PERIOD .))