"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," Carr said in a statement obtained by CNBC.
READ MORE: Trump Says to 'Probably' Answer Some Mueller Questions as Part of Russia Probe
According to US media reports, a woman who previously worked with Mueller claims that a Republican activist offered her thousands of dollars to accuse Mueller of sexual misconduct and workplace harassment.
Special Counsel Robert Mueller is investigating claims of Russian meddling in the 2016 election, as well as alleged collusion between Moscow and then-candidate Donald Trump's campaign.
Russia and Trump have repeatedly denied allegations of collusion, and Moscow has called the accusations of interference in the election "absurd."