Probing a lobby full of lobbyists

Federal prosecutors in New York have their hands full when it comes to investigating potentially shady lobbyists, thanks to special counsel Robert Mueller.

Mueller has referred a series of cases to the U.S. Attorney's Office for the Southern District of New York involving several high-profile American lobbyists and operatives who failed to register as foreign agents, CNN first reported Tuesday.

Longtime Democratic lobbyist Tony Podesta, former Minnesota Republican Rep. Vin Weber and his work for Mercury Public Affairs and Obama White House counsel Greg Craig, a former partner at law firm Skadden, Arps, Slate, Meagher & Flom LLP, are all part of the inquiry, per reports.

No charges have been filed against the trio.

All three men and their firms have been mentioned in relation to Paul Manafort, Trump's one-time campaign chief who is currently on trial for money laundering, tax evasion and conspiracy.

CNN noted that Manafort and his business partner Rick Gates paid the Podesta Group and Mercury Public Affairs through a nonprofit called the European Centre for a Modern Ukraine. The group was attempting to bolster the image of the pro-Russian Ukrainian government in power between 2012 and 2014.

Manafort and Gates were charged by the special counsel's office with failing to file as foreign agents for their work in Ukraine. Gates accepted a plea deal.

Podesta's firm and Mercury were paid more than $1.1 million each for their work, according to The New York Times. But neither registered their work with the Justice Department, which would have required them to detail their lobbying activities.

A lawyer who worked for the same firm as Craig, Alex van der Zwaan, pleaded guilty to lying to investigators from the special counsel's office in February.

Van der Zwaan admitted to misleading the special counsel's office about his discussions with a senior partner at the firm regarding their work in Ukraine.