Special counsel Robert Mueller's investigators are probing $16 million in bank loans obtained by Paul Manafort – and whether the former Trump campaign chair offered the banker who oversaw them an administration job in return.

Manafort obtained the loans using his pricey New York and Virginia residences as collateral immediately after leaving the Trump campaign amid reports about his dealings with a pro-Moscow Ukrainian political party.

NBC reported that Mueller is investigating whether Manafort promised a job to Chicago banker Stephen Calk, the head of the lender, Federal Savings Bank, in return.

Prosecutors referenced 'additional criminal conduct' in response to a Manafort motion relating to his bail at a hearing on Friday.

Investigators are probing $16 million in bank loans obtained by Paul Manafort – and whether the former Trump campaign chair offered the banker who oversaw them an administration job in return

They brought up 'additional criminal conduct that we have learned since the Court’s initial bail determination." This included turning in financial statements for his lobbying firm 'overstating its income by millions of dollars.'

"That criminal conduct includes a series of bank frauds and bank fraud conspiracies," according to the government.

"At the next bail hearing, we can proffer to the Court additional evidence related to this and the other bank frauds and conspiracies, which the Court may find relevant to the bail risk posed by Manafort,' prosecutors wrote in opposition to his bail proposal, and charging that he puffed up his income and assets to obtain a $9 million mortgage.

Calk was given a role on Trump's campaign Council of Economic Advisors, but failed to land a job in the administration.

Stephen Calk, chair of Federal Savings Bank, was given a role on Trump's campaign Council of Economic Advisors, but failed to land a job in the administration

Former Trump campaign chairman Paul Manafort departs the federal court house after a status hearing in Washington, DC, USA, on 14 February 2018

Sources told NBC other bank loan officers questioned the loans obtained by Manafort, and a source said at least one bank employee felt pressure to approve them, and is cooperating with authorities.

The sources say the three loans were questioned by other officials at the bank, and one source said that at least one of the bank employees who felt pressured into approving the deals is cooperating with investigators.

NBC cited FDIC records showing the loans made up 5 per cent of the bank's loans.

CitiMortgage sued another bank Calk ran, Chicago Bankcorp, in 2014 for $4.5 million in damages, alleging the bank sold it underwriting information on bank loans with inaccurate information.

Special counsel Robert Mueller's prosecutors referenced 'additional criminal conduct' in response to a Manafort motion relating to his bail at a hearing on Friday

Manafort got loans totaling $16 million using New York and Virginia properties as collateral. His Brooklyn brownstone is pictured here

Manafort got multiple loans from the bank through an LLC he created the day he left the Trump campaign in August 2016 - Summerbreeze, LLC.

Loans for a Brooklyn property totaled $6.5 million, and the total his $16 when loans on properties from the bank in Arlington, Virginia and the Hamptons are included.

Prosecutors filed new sealed criminal charges in the case against Manafort and his former deputy Rick Gates on Wednesday.

The document ran just a single page and didn't state what the new charges are. It may be a superseding indictment, the AP reported.