Special Counsel Robert Mueller has apparently subpoenaed Germany's Deutsche Bank to obtain documents about its dealings with President Trump and his family, Bloomberg Politics reported Tuesday. The investigation is part of Mueller's larger probe into Russia's role in the 2016 presidential election.

Trump reportedly owes more than $300 million to Deutsche Bank, with Rep. Maxine Waters (D-Calif.) having attempted multiple times this year to learn if the loans have any connection to Russia. "The fact remains that more than four months after we initially called on you to investigate Deutsche Bank's Russian money-laundering scheme, we still do not know who participated or benefited, or whether the scheme was related to the broader money-laundering scheme known as 'The Global Laundromat,'" Waters wrote in a letter to Deutsche Bank's CEO, John Cryan, in August.

Deutsche Bank was one of the only financial institutions willing to lend to Trump. "Other Wall Street banks, after doing extensive business with Mr. Trump in the 1980s and 1990s, pulled back in part due to frustration with his business practices but also because he moved away from real-estate projects that required financing," officials told The Wall Street Journal.

Trump has warned that he considers any probe by Mueller into his family's finances to be "a violation" unless it is directly related to Russia. Due to recent charges against Paul Manafort and Michael Flynn, some Senate Democrats have said Mueller's moves appear to be building a potential obstruction of justice case against Trump himself, Bloomberg Politics writes. Jeva Lange