(S (S (NP (BASENP (DT The) (NN cause)) (PP (IN of) (BASENP (DT the) (NN fire)))) (VP (VP (VP (VBZ is) (RB not)) (VBN known)) (CC and) (VP (VBZ is) (PP (IN under) (BASENP (NN investigation)))))) (PERIOD .))