(S (S (BASENP (PRP They)) (VP (VBD were) (VP (ADVP (RB subsequently)) (VP (VBN killed) (PP (IN after) (S (VP (VBG being) (VP (VBN trapped) (PP (IN by) (NP (NP (BASENP (DT a) (NN fire)) (PP (IN in) (BASENP (DT the) (NN mine)))) (SBAR (WHNP (WDT which)) (S (VP (VP (VBD prevented) (BASENP (PRP them))) (PP (IN from) (S (VP (VBG escaping))))))))))))))))) (PERIOD .))