George Papadopoulos, a former foreign policy adviser to U.S. President Trump’s presidential campaign, pleaded guilty to lying to the FBI about contact with a Russian with ties to Kremlin officials, according to an indictment unsealed on Monday.

Papadopoulos admitted to lying in a January interview with the FBI about his contacts in London with a Russian professor, “whom he understood to have close connections with senior Russian government officials,” according to the court filing.

According to the court documents, Papadopoulos, in the January interview, said he had met with the professor before joining the campaign. However, he actually met with her days after joining the campaign, and the professor only took interest in him because of his status with the campaign, according to prosecutors.

Papadopolous admitted that the professor had told him the Russians had “dirt” on Hillary Clinton in the form of “thousands of emails.”

The news comes as Mueller’s investigation unveiled indictments of two Trump associates on Monday: Paul Manafort and his longtime associate Rick Gates.