(S (S (PP (IN As) (NP (BASENP (NN part)) (PP (IN of) (NP (BASENP (DT the) (JJ recent) (NNS releases)) (PP (IN by) (NP (BASENP (DT the) (NNP NTSB)) (CC and) (BASENP (NNP AAIB)))))))) (S (BASENP (PRP it)) (VP (VBZ has) (VP (VP (VBN become) (ADJP (JJ apparent))) (SBAR (IN that) (S (NP (BASENP (NNS investigators)) (PP (IN from) (NP (BASENP (DT both) (NNS bodies)) (PRN (COMMA ,) (SBAR (WHNP (WDT which)) (S (VP (VBP are) (VP (VBG collaborating))))) (COMMA ,))))) (VP (VBP have) (VP (VBN found) (SBAR (S (NP (BASENP (NN ice) (NN buildup)) (PP (IN in) (BASENP (DT the) (NN fuel) (NN system)))) (VP (VBD caused) (BASENP (DT both) (NNS rollbacks))))))))))))) (PERIOD .))