(S (S (S (NP (BASENP (DT The) (NN blast)) (COMMA ,) (SBAR (WHNP (WDT which)) (S (VP (VBD occurred) (PP (IN at) (NP (NP (BASENP (NN 4:30) (NN a.m.)) (BASENP (NN EEST))) (PRN (LRB -LRB-) (BASENP (NN UTC) (NN +3)) (RRB -RRB-)))))))) (VP (VBZ is) (VP (VBN believed) (S (VP (TO to) (VP (VB have) (VP (VBN been) (VP (VBN caused) (PP (IN by) (BASENP (JJ excessive) (NN summer) (NNS temperatures))))))))))) (CONJP (COMMA ,) (CC but)) (S (BASENP (JJ other) (NNS reports)) (VP (VBP suggest) (SBAR (IN that) (S (BASENP (DT a) (NN gas) (NN leak)) (VP (MD may) (VP (VB have) (VP (VBN sparked) (BASENP (DT the) (NN blast)))))))))) (PERIOD .))