Wall Street firms including Bank of America Corp. , Citigroup Inc., Deutsche Bank AG , JPMorgan Chase & Co., Morgan Stanley and Wells Fargo & Co. have recently provided the documents to congressional investigators, according to people familiar with those probes. The investigators are working on a joint probe into potential foreign influence on Mr. Trump and his family by the House Financial Services Committee and the House Intelligence Committee. More information will likely be handed over in coming weeks as the banks continue to respond to subpoenas sent in April, the people said…

Ms. James’s office has also in recent weeks received financing documents and emails from Investors Bancorp Inc., the people said. The Short Hills, N.J., regional bank handed over thousands of pages in response to a civil subpoena demanding information on a 2010 mortgage on Trump Park Avenue, a condominium building in Manhattan owned by Mr. Trump, the people said…

The legal fights “could drag on for months, if not years—and that of course is the president’s strategy,” said Saikrishna Prakash, a law professor at the University of Virginia. “The Democrats are seeking to investigate, embarrass the president, and he’s trying to delay his personal finances becoming public.”