They said they had no "evidence" of a connection.
So it appears that you fail Logic 101. The lack of evidence (i.e., of a connection) is not positive proof of a non-connection.
As Rummy has said before, there are
(1) the things you know you know,
(2) the things you know you don't know, and
(3) the things you don't know you don't know.
We are "officially" in #3 land on this question, although we may "know" and are not telling yet.
And, oh-by-the-way, there is plenty of circumstantial evidence, as has been pointed out here.
Washington-speak has, post Janet Reno, apparently required that any evidence less than a smoking gun must be called "no evidence", although I don't understand why Rummy and the Bush people don't flat-out reject that bromide -- I suspect that they've thought it through, gamed it out, and concluded that the press will outspin them if they try to re-assert a normal understanding of the word.