(S (S (S (BASENP (DT The) (NNS sailors)) (VP (VBD had) (VP (VBN been) (VP (VP (VP (VBN captured) (PP (IN in) (BASENP (DT the) (NNP Niger) (NNP Delta)))) (PP (IN from) (NP (BASENP (PRPD their) (NN vessel)) (COMMA ,) (BASENP (DT the) (NNP BBC) (NNP Polonia))))) (COMMA ,) (PP (ADVP (RB apparently)) (PP (IN by) (NP (BASENP (NN one)) (PP (IN of) (NP (BASENP (DT the) (JJ numerous) (JJ armed) (JJ militant) (NNS groups)) (PP (IN in) (BASENP (DT the) (NN area)))))))))))) (COMMA ,) (SBAR (IN although) (S (BASENP (DT no) (NN one)) (VP (VBZ has) (VP (ADVP (RB yet)) (VP (VBN claimed) (BASENP (NN responsibility)))))))) (PERIOD .))