Special counsel Robert Mueller's team is looking into millions of dollars that was donated to President Trump's inauguration fund by people who have connections to Russia, Saudi Arabia, the United Arab Emirates, and Qatar, according to a report Friday.

Mueller's federal investigators have questioned real estate mogul Thomas Barrack, who was in charge of fundraising for the inauguration festivities, and others involved in the process about donors, ABC News reported.

Any donor with business or personal connections with people or companies in any of those four nations is being brought in for questioning before the special counsel. Some of those donors had given more than $1 million each to the inauguration.

Investigators have zeroed in on U.S. businessmen Leonard Blavatnik and Andrew Intrater. Both men have business connections with Russian entities.

Barrack raised $107 million for the January 2017 event, double what former President Barack Obama hauled in during his first inauguration in 2009.