Special Counsel Robert Mueller’s investigation has begun interviews with Republicans National Committee staffers about the committee’s digital operations during the 2016 election, Yahoo News reported Wednesday.

According to Yahoo News’ Michael Isikoff, Mueller’s team is examining whether the joint digital operation between the RNC and President Trump’s campaign “was related to the activities of Russian trolls and bots aimed at influencing the American electorate.”

The report is based on two sources familiar with Mueller’s investigation.

The RNC did not to TPM’s inquiry, while a spokesperson for the special counsel declined to comment.

Whether Russia’s election meddling on social media was coordinated with the Trump campaign or its allies has been a questioned floated by the Democratic lawmakers probing the issue. In public interviews, representatives from social media companies have played coy when asked the question and merely have confirmed that they were handing all the relevant data to congressional investigators. The tech companies in question have reportedly also been cooperating with Mueller’s probe.

Cambridge Analytica, a data company that also worked with the Trump campaign, has come under the scrutiny of the congressional investigations. Company CEO Alexander Nix reportedly offered to help Wikileaks founder Julian Assange organize the hacked Democratic emails the website had been publishing, but Assange has denied accepting Nix’s entreaty.