(S (S (BASENP (NNS Officials)) (VP (VBP say) (SBAR (SBAR (S (NP (BASENP (DT the) (NN crash)) (PRN (COMMA ,) (SBAR (WHNP (WDT which)) (S (S (VP (VBD occurred))) (SBAR (WHADVP (WRB when)) (S (BASENP (DT the) (NN plane)) (VP (VBD was) (VP (VP (VBG approaching) (BASENP (DT a) (JJ Russian) (NN airport))) (PP (IN on) (BASENP (NNP Saturday))))))))) (COMMA ,))) (VP (VBD was) (PP (JJ due) (PP (TO to) (BASENP (JJ dense) (NN fog))))))) (CONJP (COMMA ,) (CC and)) (SBAR (IN that) (S (BASENP (EX there)) (VP (VBP are) (BASENP (DT no) (NNS survivors)))))))) (PERIOD .))