While the evidence of Iranian involvement is strong, there are also signs that al Qaeda played some role, as yet unknown.
( ( While ( ( ( the evidence ) ( of ( Iranian involvement ) ) ) ( is strong ) ) ) ( , ( there ( ( ( are also ) ( signs ( that ( ( al Qaeda ) ( ( ( played ( some role ) ) , ) ( as ( yet unknown ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN While) (S (NP (NP (DT the) (NN evidence)) (PP (IN of) (NP (JJ Iranian) (NN involvement)))) (VP (VBZ is) (ADJP (JJ strong))))) (, ,) (NP (EX there)) (VP (VBP are) (ADVP (RB also)) (NP (NP (NNS signs)) (SBAR (IN that) (S (NP (NNP al) (NNP Qaeda)) (VP (VBD played) (NP (DT some) (NN role)) (, ,) (SBAR (IN as) (S (ADVP (RB yet)) (ADJP (JJ unknown))))))))) (. .)))
The evidence proving Iranian involvement is absolutely trustworthy.  
( ( ( The evidence ) ( proving ( Iranian involvement ) ) ) ( ( is ( absolutely trustworthy ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN evidence)) (VP (VBG proving) (NP (JJ Iranian) (NN involvement)))) (VP (VBZ is) (ADJP (RB absolutely) (JJ trustworthy))) (. .)))