The top Democrat on the Senate Intelligence Committee said Thursday that he will not jump to conclusions in the panel’s investigation into Russian election meddling, but said “so far there is a great, great deal of smoke.”

The remarks from Virginia Democratic Sen. Mark Warner came at the opening of the committee’s hearing on Russian intelligence operations to interfere in the 2016 U.S. presidential race. The panel is conducting an investigation into Moscow’s meddling, including possible ties between Russia and the Trump campaign.

The House Intelligence Committee is carrying out a parallel inquiry, although that probe has become mired in partisan rancor after the chairman, Devin Nunes, bypassed Democrats to go to the press and the White House with claims of alleged incidental monitoring of the Trump transition team.

In a nod to the turmoil engulfing the House investigation, the chairman of the Senate committee, North Carolina Republican Richard M. Burr said his panel must avoid such partisan sniping for the Senate inquiry to succeed.

“If we politicize this process, our efforts will likely fail,” Burr said in his opening statement.

Warner, echoing Burr, said the panel “simply must — and we will — get this right.” He said the full committee agrees “it is vitally important that we do this in as credible, bipartisan and transparent a manner as possible.”

The Virginia Democrat said it was critical that the investigation succeed because Russia continues to employ the methods it used to interfere in the U.S. vote against America’s friends overseas.

“Some of our close allies in Europe are experiencing exactly the same kind of interference in their political processes,” Warner said. “Germany has said its parliament has been hacked. French presidential candidates have been the subjects of Russian propaganda and disinformation.”

The committee’s hearing Thursday involves two panels of outside experts, and focuses on Russia’s historical use of so-called active measures to influence political campaigns abroad.