The evidence the Trump campaign colluded with Russian operatives is more than circumstantial, Rep. Adam Schiff, the ranking Democrat on the House Intelligence Committee, said Tuesday. The comments followed a news conference by committee Chairman Devin Nunes at which he announced a “source” had given him evidence information was collected incidentally on Trump transition team members as part of other ongoing national security investigations.

“I can tell you that the case is more than that [circumstantial evidence],” Schiff told MSNBC. “And I can’t go into the particulars, but there is more than circumstantial evidence now.”

Schiff, D-Calif., declined to go into specifics but said the evidence is “worthy of investigation and that is what we ought to do.”

Read: Did Paul Manafort Commit Treason?

The FBI has been investigating links between the Trump campaign and Russia since late July, FBI Director James Comey revealed in testimony Monday before the intelligence panel. Russia is suspected of being behind the hacks of the Democratic National Committee’s emails and other actions designed to undermine Democratic presidential candidate Hillary Clinton.

President Donald Trump has said he was unaware of any contacts between his campaign and Russian operatives, but former campaign Chairman Paul Manafort is under investigation for his work on behalf of Russian oligarch Oleg Deripaska.

Read: Prominent Trump Aid Tied To Russian DNC Hacking Denies Efforts To Influence Election

Schiff called for an independent commission to investigate the alleged ties following Nunes decision to brief the president on what the committee knows. Sen. Joe Manchin, D-W.Va., agreed, saying the decision raises concerns about Nunes ability to be impartial.

Nunes, R-Calif., said U.S. intelligence agencies intercepted conversations of Trump’s transition team, and perhaps Trump himself, inadvertently after the November election. He told a news conference a “source” gave him evidence of the surveillance.

“I have seen intelligence reports that clearly show that the president-elect and his team were, I guess, at least monitored,” Nunes said. “It looks to me like it was all legally collected, but it was essentially a lot of information on the president-elect and his transition team and what they were doing.” None of the information, he said, was related to Russia.

Nunes remarks followed earlier statements he made saying he had seen no evidence Trump was wiretapped as did his counterpart on the Senate Intelligence Committee. At his news conference, he did not cite any specific evidence but did reiterate there had been no “wiretap” on Trump Tower.

Nunes has yet to brief members of his committee.

Trump seized on Nunes comments, saying he felt “somewhat” vindicated during a brief pool spray before a meeting with the Congressional Black Caucus at the White House. Trump issued a series of tweets March 4, accusing former President Barack Obama of ordering wiretaps on Trump Tower. Trump has called the whole controversy over alleged Russian ties “fake news.”