(S (S (BASENP (PRP They)) (VP (VBD were) (PP (VP (VBN trapped) (PP (IN since) (NP (NP (BASENP (NN 6:40) (NN am)) (BASENP (NNP Eastern))) (COMMA ,) (NP (BASENP (NNP Monday)) (COMMA ,) (BASENP (NNP January) (NN 2)))))) (PP (VBG following) (NP (BASENP (DT a) (NN methane) (NN gas) (NN explosion)) (SBAR (WHNP (WDT which)) (S (VP (VBD caused) (S (BASENP (DT the) (NN shaft)) (VP (TO to) (VP (VB collapse)))))))))))) (PERIOD .))