Idaho Sen. Jim Risch told the PBS Newshour Tuesday that the Senate’s investigation of Russian interference in the U.S. presidential election would expand to look at ousted National Security Adviser Michael Flynn’s contacts with the Russian ambassador in December.

But he declined to say whether Senate Intelligence Committee would look into whether President Trump had direct knowledge of Flynn’s discussions with Ambassador Sergey Kislyak regarding U.S. sanctions against Russia. The sanctions were imposed by President Obama at the end of December after intelligence service confirmed Russian efforts to hack the election.

Flynn resigned Monday as the president’s top security adviser amid disclosures that he sought to undermine the former administration’s actions and then lied about it to members of Trump administration, including Vice President Mike Pence.

“There’s already been an investigation started on the Russian situation,” Risch, a Republican who serves on the Intelligence committee, told Newshour host Judy Woodruff. “Obviously with what’s happened that net is wide enough” to include Flynn’s actions, he said.

But he demurred when Woodruff pressed him on whether the committee would investigate the president’s actions, calling it “a very delicate situation between two branches of government.”

“It sounds like you’re not saying whether or not the committee’s going to look into the president’s handling of this,” Woodruff said.

“I think that’s a different inquiry as to whether conversations were condoned,” Risch said. “I’m very reluctant to talk about a collision between the two branches of government on something like this.”

Woodruff also interviewed Sen. Mark Warner, D-Virginia, the committee’s ranking member, who said an investigation of whether the president knew of Flynn’s actions was “further down the path.”

“We have to start with what Flynn said to the Russian ambassador,” Warner said. “I hope and pray that it’s not the case that the president was somehow aware of these conversations.”

The Senate committee’s probe, Warner said, is focused on three areas: contacts between Russians and Trump contacts before and after the election, now including Flynn’s talks with Kislyak in December; the “unprecedented” fake news campaign to influence the election, which he said involved as many as “1,000 Russian internet trolls”; and the hacking of email accounts held by the Democratic National Committee and John Podesta, a top adviser to Hillary Clinton.

Risch also discussed Flynn’s resignation on Fox News.