Robert Mueller, the special counsel in charge of the Russia probe, plans to interview current and former senior Trump administration officials as part of his ongoing investigation, according to a new report on Saturday.

Mueller is reportedly looking to interview former administration officials including Reince Priebus, who recently resigned as White House chief of staff, three sources close to the discussions told the New York Times.

Mueller is asking for records including details of specific meetings with administration and campaign officials, and any related documents such as transcripts. The meetings he's asking about include those related to President Trump's decision to fire former FBI Director James Comey, according to the report.

Priebus would likely know a number of specifics about all meetings in the White House.

Mueller recently assembled a grand jury as part of the investigation, which has the power to subpoena records and ask for witness testimonies on the case.

The investigation encompasses Russian interference in the 2016 U.S. election and any possible collusion between members of Trump's campaign or administration and Moscow.

Mueller's interest in Trump's senior advisers, especially those who have revealed meetings with Russian officials during the campaign, was expected. However, it is further indication that his probe is expansive and becoming more intense.

Ty Cobb, a special counsel to the president, told the paper the White House would "continue to fully cooperate" with Mueller's investigation.

-This report was updated at 1 p.m.