U.S. Sen. Angus King of Maine said Sunday he is “deeply troubled” by reports that the chairman of the Intelligence Committee he serves on was enlisted by the White House to spin reporters on alleged ties between Russian intelligence operatives and the Trump presidential campaign.

King, who has previously championed having the Senate Intelligence Committee spearhead investigations into alleged Russian influence in the 2016 election, said he would “have serious concerns if it seems we are no longer able to proceed in this matter” because of lost credibility.

Numerous Democrats and at least one Republican in Congress have called for the formation of an independent committee or the appointment of a special prosecutor to investigate Russian involvement, but Maine’s senators have not been among them. Thus far the Republican leadership in both chambers has left the task with the respective chambers’ intelligence committees.

The Washington Post reported Friday that the White House had the chairmen of the Senate and House intelligence committees – Sen. Richard Burr, R-N.C., and Rep. Devin Nunes, R-Calif. – place calls to reporters challenging stories by CNN and The New York Times alleging regular contact between the Trump campaign and Russian intelligence officials.

Both legislators acknowledged to the Post that they had made the calls.

“I’ve had those conversations,” Burr told the Post. “I felt I had something to share that didn’t breach my responsibilities to the committee in an ongoing investigation.”

King, an independent who caucuses with Democrats, said in a written statement Sunday afternoon that he intends “to speak with Chairman Burr to better understand what happened. This committee must have credibility not only with our colleagues, but also with the American people – to whom we owe nothing less than a thorough, fair and nonpartisan investigation – and I will have serious concerns if it seems that we are no longer able to proceed in this matter.”

Republican Sen. Susan Collins of Maine – who also sits on the Intelligence Committee – issued a statement Sunday night reiterating the committee’s competence and “bipartisan determination” to carry out the investigation and emphasizing the importance of its members working in an uncompromised fashion.

“For the public to have confidence in our findings, it is important that the committee work in a completely bipartisan fashion and that we avoid any actions that might be perceived as compromising the integrity of our work,” Collins said in the statement, adding that the panel should issue a public report on its findings.

Like King, Collins has previously rejected the need for an independent committee, telling the Portland Press Herald that the intelligence committees had “the oversight authority, appropriately cleared staff, and responsibility” to do a thorough investigation.

She reiterated this position in a radio interview Wednesday, saying the Senate Intelligence Committee would “get to the bottom of this” and pledging to hold public hearings and to call on former National Security Adviser Michael Flynn to testify. Flynn resigned after misleading Vice President Mike Pence about the content of his pre-inaugural conversations with the Russian ambassador to the U.S.

Maine’s 1st Congressional District representative, Chellie Pingree, is one of 195 House Democrats who have signed on to a bill to create an independent, bicameral commission to investigate the alleged Russia contacts, and in January asked outgoing Attorney General Loretta Lynch to appoint a special prosecutor to look into the matter.

Pingree also expressed concern over the reports about Burr and Nunes countering news reports at the White House’s request.

“This raises serious red flags and multiplies the existing questions about the ability of Congress to do an independent investigation,” she said in a written statement Sunday night.

Pingree also praised Republican Rep. Darrell Issa of California – a Trump supporter – for calling for the creation of a special prosecutor on HBO’s “Real Time with Bill Maher” on Friday night. Issa had said it would be improper for Trump’s attorney general, Jeff Sessions, to lead the investigation because he had served in the Trump campaign and was a presidential appointee.

A spokesman for Rep. Bruce Poliquin, who represents Maine’s 2nd District, did not directly respond to questions about whether he had concerns that the latest developments might have compromised the House and Senate intelligence committees’ ability to do a thorough and independent investigation.

“The congressman will continue to follow the (Senate Intelligence) Committee’s efforts on this matter,” spokesman Brendan Conley said in a written statement.