An alleged scheme to pay women to fabricate claims of sexual assault against special counsel Robert Mueller has been referred to the FBI, the special counsel's office confirmed to CBS News.

"When we learned last week of allegations that women were offered money to make false claims about the special counsel, we immediately referred the matter to the FBI for investigation," special counsel spokesman Peter Carr said in a statement to CBS News. The special counsel's office did not go into detail about the allegations or who is behind them.

At the same time, in a Facebook video posted Tuesday, right-wing Newsmax host and lobbyist Jack Burkman claimed a "number of women" allege Mueller perpetrated sexual assault. Burkman claimed the first of the women will "unveil a very bad sexual assault" at a news conference Thursday at noon.

Get Breaking News Delivered to Your Inbox

The Atlantic reported Tuesday that the special counsel learned of the scheme from several journalists who had been contacted by a woman who alleged that a man claiming to work for Burkman offered her about $20,000 to accuse Mueller of sexual misconduct and harassment. The woman told the Atlantic that she had worked for Mueller as a paralegal decades ago. Mueller, she said, "was always very polite" and "never inappropriate."

In May, Burkman offered a reward for damaging information about Mueller, and during the confirmation process for now-Justice Brett Kavanaugh, he offered a $25,000 reward for damaging information about Kavanaugh's accusers.

Mueller is investigating Russian election meddling and any ties to Trump associates. The president has declared Mueller's probe is "illegal" and a "witch hunt," and some supporters of the president have attempted to discredit Mueller's investigation.

This is a developing story and will be updated.

— CBS News' Andres Triay and Steven Portnoy contributed to this report