(S (S (NP (BASENP (DT The) (NN fire)) (PRN (COMMA ,) (SBAR (WHNP (WPD whose) (NN cause)) (S (VP (VP (VBZ is) (RB not)) (VP (ADVP (RB yet)) (VBN known))))) (COMMA ,))) (VP (VP (VBD burned) (PP (IN for) (NP (BASENP (QP (RB around) (DT an)) (NN hour)) (CC and) (BASENP (QP (DT a) (NN half)))))) (PP (IN before) (S (VP (VBG being) (VP (VBN extinguished))))))) (PERIOD .))