By Manu Raju and Tom LoBianco CNN

WASHINGTON (CNN) -- The speaker of the House, the Senate Intelligence Committee chairman and the ranking Democrat on the committee said Thursday that they've seen no evidence of President Donald Trump's accusation that he was wiretapped last year by his predecessor.

Senate Intelligence Committee chair Richard Burr and ranking member Mark Warner issued a statement Thursday, saying "based on the information available to us, we see no indications that Trump Tower was the subject of surveillance by any element of the United States government either before or after Election Day 2016."

The statement from the leaders of the Senate Intelligence Committee marks the clearest and strongest refutation of Trump's allegations since the President first made them two weeks ago. The senators statement also addresses Trump's more recent statement that he was not merely speaking about wiretapping specifically.

The leaders of the House Intelligence Committee have said they have yet to see any evidence of wiretapping, but have yet to flatly rule out all surveillance. House Intelligence Chairman Devin Nunes said Wednesday that it was possible that Trump aides were surveilled via "incidental" collection.

Ranking Democrat of the House committee Adam Schiff told CNN that he expects FBI Director James Comey to also say that he's seen no evidence of Trump's claim when the director testifies before his committee Monday.

"Because there's no evidence of this at all," Schiff told CNN. "But again you can see the President trying to say, 'Well I didn't mean what I said or what I said could mean various different things' --- he was very specific in what he said. So we'll ask the director to address that very specific allegation."

Their statement came hours after House Speaker Paul Ryan said that "no such wiretap existed," citing intelligence reports to House leaders.

"The intelligence committees, in their continuing, widening, ongoing investigations of all things Russia, got to the bottom -- at least so far with respect to our intelligence community -- that no such wiretap existed," Ryan said in response to a question from CNN at a news conference.

Ryan's comment follows Trump and the White House retreating from the President's stunning accusation in a tweet two weeks ago.

"When I say wiretapping, those words were in quotes. That really covers -- because wiretapping is pretty old-fashioned stuff -- but that really covers surveillance and many other things. And nobody ever talks about the fact that it was in quotes, but that's a very important thing," Trump told Fox News Wednesday.

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