WASHINGTON (Reuters) - Prominent Washington lobbyist Tony Podesta has stepped down from his lobbying firm Podesta Group as investigators’ examine his company’s ties to U.S. President Donald Trump’s indicted former campaign manager, a source familiar with the matter said on Monday.

Podesta stepped down on the same day federal investigators probing Russian interference in the 2016 U.S. election campaign charged former Trump campaign manager Paul Manafort and a business associate, Rick Gates, with money laundering.

Manafort, a longtime Republican operative, and Gates pleaded not guilty to a 12-count indictment with charges ranging from money laundering to acting as unregistered agents of Ukraine’s former pro-Russian government.

The indictment against Manafort and Gates listed two unnamed firms as “Company A” and “Company B” that lobbied several lawmakers on behalf of Ukraine at Manafort’s request.

The indictment did not name Podesta Group.

A spokesperson for the Podesta Group said after Podesta stepped down on Monday that it had been in contact with investigators on special counsel Robert Mueller’s team and was fully cooperating with the probe.

The spokesperson also said the Podesta Group fully complied with the law in disclosing its lobbying on behalf of the European Centre for a Modern Ukraine, a group linked to Manafort and named in the indictment.

Podesta Group filed lobbying disclosures with the Department of Justice in April and August saying it did work in 2012 for the same pro-Russian Ukrainian group for which Manafort had worked. Podesta Group work alongside another Washington lobbying firm, Mercury LLC, which also said on Monday that it was cooperating with Mueller’s team.

No charges were filed against anyone with Podesta Group or Mercury.

Tony Podesta did not respond to requests for comment on Monday. Podesta was the head of the firm that bore his name. It did $10.7 million in lobbying in the first nine months of 2017, according to disclosures the firm filed with the U.S. Congress.

He is the brother of John Podesta, who served as chairman of the presidential campaign of Democratic candidate Hillary Clinton, and as a senior White House adviser to Democratic former President Barack Obama.

Mueller’s team has been investigating alleged Russian meddling in the 2016 campaign, but neither Trump nor the campaign were mentioned in the indictment against Manafort and Gates.

While Podesta Group is seen as a mainly Democratic lobbying firm, Mercury is viewed as mainly a Republican shop. Mercury is a subsidiary of Omnicom Group and does public relations work in addition to lobbying. Omnicom did not reply to a request for comment.

Podesta is listed as a lobbyist on several of the firm’s largest accounts including Wells Fargo, Lockheed Martin, Oracle, Wal-Mart, Textron and General Dynamics.

Wells Fargo, Wal-Mart, Oracle, General Dynamic and Lockheed Martin all declined to comment. Textron did not respond to a request for comment.