(S (S (BASENP (JJ Earlier) (JJ unconfirmed) (NNS reports)) (VP (VBD had) (VP (VBN said) (SBAR (S (BASENP (DT the) (NN debris)) (VP (MD could) (VP (VB have) (VP (VBN been) (NP (BASENP (DT the) (NN result)) (PP (IN of) (NP (BASENP (DT a) (JJ small) (NN plane)) (VP (VBG exploding))))))))))))) (PERIOD .))