The U.S. Treasury Department is probing the offshore financial transactions of former Trump campaign chairman Paul Manafort as part of a federal anti-corruption probe into his work in Ukraine.

Information related to the transactions was turned over earlier this year to the department's Financial Crimes Enforcement Network by investigators in Cyprus, reported The Associated Press.

A source familiar with the case told the AP that the Treasury Department requested the documents, and the Cyprus attorney general was made aware of the U.S. request.

Federal prosecutors began looking into Manafort's paid work for the pro-Russian Party of Regions as part of a broader investigation into stolen Ukrainian assets after the nation's Vladimir Putin-aligned President Viktor Yanukovych was ousted in 2014.

The AP reported earlier this week that Manafort secretly developed a plan to advance Putin's interests in the U.S. in 2005, a year before he moved into Trump Tower.

Manafort quit the Trump campaign in September as questions began to swirl about his work in Ukraine, and his ties to the Putin regime have raised new questions as the FBI investigates possible collusion between President Donald Trump's campaign and the Russian government.

Financial records obtained by the AP show Manafort sometimes routed financial transactions through Cypriot shell companies, including a $19 million deal in 2014 with Russian billionaire Oleg Deripaska to buy Ukrainian cable television provider Black Sea Cable.

Deripaska, a Russian aluminum magnate and close ally of Putin, said afterward that Manafort and his associates refused to tell him how the money had been used.

Manafort pitched a "confidential plan" in 2005 to Deripasko to promote Russian interests through U.S. media, and the AP reported that he signed a $10 million annual contract with the oligarch -- with whom he maintained a business relationship until "at least" 2009.

The Republican political strategist also reportedly tried to help Deripaska obtain a U.S. visa in 2000 over objections by the FBI, which believed the billionaire had lied to agents during an interview.

The AP found in another case that a Manafort-linked company received $1 million in October 2009 from mysterious firm through the Bank of Cyprus, which Trump's Commerce Secretary Wilbur Ross oversaw as vice chairman from 2014 until his Senate confirmation.

The White House was accused of withholding information from Congress about whether Trump or his campaign affiliates had ever received loans through the bank, which is partially owned by Viktor Vekselberg and Vladimir Strzhalkovsky -- two longtime Putin allies.

Ross verbally denied any knowledge of such transactions, but the White House refused to release a written response to a query from Democratic senators.

The AP reported that Manafort's mysterious transaction more than seven years ago was split in half the same day the payment went through the Bank of Cyprus and were disbursed in two payments of $500,000 to accounts with no obvious owner.

Cyprus had a well-known history of money laundering before joining the European Union in 2004.

A Ukrainian lawmaker released other financial documents earlier this week from the Party of Regions' so-called "black ledger" that show Manafort laundered those payments using offshore accounts in Belize and Kyrgyzstan.

Serhiy Leshchenko, a Ukrainian lawmaker and investigative journalist, released a copy of an invoice on Manafort’s consulting company letterhead that shows a payment of $750,000 for the sale of computers to a Belize-based company.

On that same day, Oct. 14, 2009, Manfort’s name is listed in a $750,000 entry in the black ledger, which was found at party headquarters during the 2014 riots, that investigators view as a party slush fund.

Manafort, who is wanted for questioning in Ukraine, accused Leshchenko of attempting to blackmail him before he stepped down from the Trump campaign.