(S (S (BASENP (JJ Initial) (NNS investigations)) (VP (ADVP (RB now)) (VP (VBP suggest) (SBAR (S (BASENP (DT the) (NN explosion)) (VP (VBD was) (VP (VBN caused) (PP (IN by) (BASENP (JJ poor) (NN ventilation)))))))))) (PERIOD .))