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New York Attorney General Letitia James' office issued subpoenas to Deutsche Bank and Investors Bank late Monday night as part of an inquiry into a set of major Trump Organization projects and Donald Trump's effort to purchase the NFL's Buffalo Bills in 2014, a source familiar with the investigation told NBC News.

Regarding Deutsche Bank, state investigators subpoenaed records including loan applications, mortgages, lines of credit and other financing transactions in connection with the Trump International Hotel in Washington, Trump National Doral in South Florida and the Trump International Hotel and Tower in Chicago, the source said.

Additionally, investigators requested records from Deutsche Bank on Trump's failed bid to buy the Bills, as Trump provided the bank with limited personal financial information in 2014 when he tried to purchase the team. The Bills were ultimately sold to businessman Terry Pegula.

The New York attorney general also subpoenaed Investors Bank, a New Jersey-based financial institution, for records tied to Trump Park Avenue, a project it backed.

The New York Times first reported on the probe.

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Deutsche Bank said in a statement, "We remain committed to cooperating with authorized investigations." Investors Bank and the Trump Organization did not immediately return requests for comment from NBC News.

Deutsche Bank has already found itself under the scrutiny of congressional investigators for its relationship with the president. For years, the Germany-based bank was one of the only major financial institutions to do business with Trump. Last year, the bank was examined by New York banking regulators, who ultimately did not take action.

The latest inquiry into the president's business dealings came as a result of congressional testimony provided by Michael Cohen, the president's former longtime attorney. Late last month, Cohen testified under oath to the House Oversight Committee that Trump inflated the worth of his assets in financial statements and provided Congress with copies of statements he said were sent to Deutsche Bank.

The latest probe by James' office is a civil investigation, as is the ongoing state probe that led to the dissolution of the Trump Foundation, the president's charity. New York law gives the attorney general broad authority to investigate businesses for fraud.

James, a Democrat, pledged to thoroughly examine the president as part of her campaign platform. After her victory, she told NBC News that her office "will use every area of the law to investigate President Trump and his business transactions and that of his family as well."

Trump has taken issue with James and her predecessors, Barbara Underwood and Eric Schneiderman, who resigned last year amid allegations of abusing women. The office has led significant investigations into the president's charity as well as Trump University, his defunct real estate education venture.

On James, Trump tweeted in December that she "openly campaigned on a GET TRUMP agenda."

"Will never be treated fairly by these people — a total double standard of 'justice,'" he added.

On Tuesday evening, Trump appeared to respond to the new inquiry when he tweeted: "New York State and its Governor, Andrew Cuomo, are now proud members of the group of PRESIDENTIAL HARASSERS."

"No wonder people are fleeing the State in record numbers," he added. "The Witch Hunt continues!"

The attorney general's office is independent from Cuomo's.