House Intelligence Committee
Former CIA Director John Brennan testifies before the House Intelligence Committee to take questions on “Russian active measures during the 2016 election campaign” in the Capitol Building in Washington, D.C., May 23, 2017. Reuters/Kevin Lamarque

Democrats in the House Intelligence Committee blocked interviews of key witnesses in the committee’s ongoing investigation into Russia’s role in the 2016 presidential election, Politico reported Thursday, citing sources. The objection was made because some witnesses did not comply with the committee's requests for documents.

The committee was due to interview 10 witnesses this month, but its senior Democrat objected the move, sources told Politico. Among those to be interviewed were foreign policy adviser Carter Page from Donald Trump’s campaign, the president’s longtime confidant Roger Stone, and former Trump campaign chairman Paul Manafort. Page and Stone are reportedly keen to appear before the panel.

Read: No Evidence Backing Trump's Wiretapping Claim, House Intelligence Committee Says

According to an unidentified senior committee aide, Rep. Adam Schiff (D-California) and Rep. Mike Conaway (R-Texas), agreed not to go ahead with the interviews until witnesses responded to the committee’s requests for documents. Conaway took over the investigation from House Intelligence Chairman Devin Nunes in April.

“Many such requests have yet to be complied with, and neither member believes that interviews should be scheduled until they are answered in full,” the senior committee aide told Politico. “Anyone suggesting that interviews should take place before the committee has a chance to review the relevant documents plainly and does not have the best interests of the investigation in mind,” he further said.

Sources told the news outlet the committee’s investigation was halted because of objections from Schiff (D-California).

“The majority and the witnesses are ready to go,” one of the sources told Politico. “But the minority continue to object claiming they aren’t ready.”

In January, the committee announced it would launch a bipartisan investigation into likely communications between Russia and the Trump campaign during the election. Ahead of the presidential poll, thousands of hacked emails of Democratic candidate Hillary Clinton's campaign chairman, John Podesta, and the Democratic National Committee were leaked. Russia was blamed for the hack, however, Moscow maintained it did not play a role in the hacking.

On Thursday, Schiff slammed Nunes for issuing subpoenas related to the Russia investigation. He said the latter was violating his recusal from the committee’s probe on Russia. Nunes had issued three subpoenas in relation to whether intelligence authorities improperly revealed Trump officials in surveillance reports.

"The Committee rules provide that the chair has to sign the subpoenas unless that authority is delegated to someone else," Schiff said in an interview with MSNBC. "That authority should have been delegated to [Rep.] Mike Conaway [R-Texas] in consultation with myself. That hasn't happened yet. I think that's a violation of the recusal by the Chairman."

"I think they're part of the White House desire to shift attention away from Russia to the unmasking," he added.

Nunes responded on Twitter, saying: "Seeing a lot of fake news from media elites and others who have no interest in violations of Americans' civil liberties via unmaskings."

In March, Nunes came under fire for reportedly sharing confidential details, including information on Trump’s associates and their alleged ties to Russia, with a source at the White House grounds. Following this, top Democrats called for his recusal for not informing the committee before doing so.