(S (S (S (BASENP (PRP It)) (VP (VP (VP (VBD was) (RB not)) (ADJP (RB immediately) (JJ clear))) (SBAR (WHNP (WP what)) (S (VP (VBD caused) (BASENP (DT the) (NN blaze))))))) (COMMA ,) (SBAR (IN although) (S (BASENP (DT an) (NN investigation)) (VP (VBZ is) (ADJP (JJ underway)))))) (PERIOD .))