WASHINGTON — A former advisor to President Donald Trump’s presidential campaign pled guilty to lying to the FBI about his contacts with a professor connected to Russian officials who claimed to have “dirt” on Hillary Clinton.

George Papadopolous, 30, entered the plea on Oct. 5, but it was unsealed on Monday.

It was part of Special Prosecutor Robert Mueller’s investigation into Russian interference into the 2016 election, and whether their was coordination by members of the Trump campaign. Also on Monday, Trump’s former campaign chairman Paul Manafort and his associate Rick Gates were indicted on 12 charges, including money laundering having to do with with work for the Ukrainian government and pro-Russian politicians, but the indictment does not mention their work for the Trump campaign.

The guilty plea entered by Papadopolous, however, does deal with his campaign activity. He pled guilty to making false statements to the FBI in an interview conducted on Jan. 27. Papadopolous acknowledged that he learned from an overseas professor with “substantial connections to Russian officials” that they had “dirt” on Clinton in the form of “thousands of emails.” But, according to the guilty plea, he falsely claimed that he learned of the information before joining the campaign in March 2016, as a foreign policy adviser. In fact, he already was working in that capacity.

Papadopolous also knew that the professor had substantial connections to Russian officials, and that the professor met with some of those officials “immediately before” telling him of the “thousands of emails.” He also “repeatedly sought to use the professor’s Russian connections in an effort to arrange a meeting between the campaign and Russian government officials,’ according to the statement of the offense made public on Monday.

It also said that Papadopolous made false statements about a meeting he had with a “certain female Russian national,” and “he sought to use her Russian connections over a period of months in an effort to arrange a meeting between the campaign and Russian government officials.”

His Jan. 27 interview with the FBI took place before Mueller was appointed as special counsel. He was arrested on July 27 at Dulles International Airport, and he then met with investigators on numerous occasions.

According to prosecutors, Papadopolous first met the professor around March 14, when he was traveling in Italy. After informing the professor that he had joined the Trump campaign, the professor told him that he had substantial connections with Russian government officials. They met again on March 24 in London, and the professor brought with him the female Russian national, and identified her as a relative of Russian President Vladimir Putin with connections to Russian officials. (In fact, she was not a relative).

In April, he sent multiple emails to others on Trump’s foreign policy team, touting his contacts with Russia and that they could help arrange a meeting between Trump and Putin. The professor also introduced Papadopolous via email to an individual in Moscow who said that he had connections to the Russian ministry of foreign affairs.

It was at a meeting on April 26 that the professor told Papadopolous about his trip to Moscow, where he met with high-level Russian officials who had “dirt” on Clinton and “thousands of emails.”

Prosecutors also noted that as Papadopolous informed the campaign about his attempts to set up a meeting between Trump and Russian officials, one campaign official informed another and wrote, “Lets discuss. We need someone to communicate that DT is not doing these trips. It should be someone low level in the campaign so as to not send any signal.”

During the summer of 2016, Papadopolous pursued an “off the record” meeting between members of the campaign and members of Putin’s office and the ministry of foreign affairs. He was later advised by a campaign supervisor to make a trip to Russia himself, but it never took place.

According to prosecutors, during his FBI interview Papadopolous also omitted the full extent of his contact with the professor and the individual with connections to the ministry on foreign affairs. But he had a Facebook account that contained information on their communications. He deactivated the account on Feb. 17, a day after the FBI interviewed him again, along with his attorney.

Papadopolous reached a plea deal with prosecutors, who will reduce its sentencing recommendation of zero to six months in prison, and a fine ranging from $500 to $9,500.

Prosecutors described Papadopolous as a “proactive cooperator,” raising speculation that he may have assisted Mueller’s team in gathering information from other targets in the investigation, perhaps even by wearing a wire to record conversations.