(S (S (S (BASENP (DT The) (NN incident)) (VP (VP (VBZ is) (ADVP (RB currently))) (PP (IN under) (BASENP (NN investigation))))) (CONJP (COMMA ,) (CC but)) (S (BASENP (NNS authorities)) (VP (VP (VBP are) (RB not)) (VP (VP (VP (VBG ruling) (PRT (RP out))) (BASENP (DT any) (NNS possibilities))) (COMMA ,) (PP (VBG including) (BASENP (JJ possible) (NN negligence))))))) (PERIOD .))