Prosecutors issued the grand jury subpoena to Fortress Investment Management late last year, the people said, as part of their wide-ranging investigation into former President Donald Trump and his company.
Investigators interest in how Trump and his company treated the Chicago loan is an expansion of an inquiry that encompasses multiple aspects of the Trump business.
Prosecutors are examining whether the company misled lenders or insurance brokers about valuations for certain properties. They are also investigating fees paid to consultants and a conservation easement taken on a New York family estate called Seven Springs.
Their interest in Fortress relates to a $130 million loan the company made to the Trump Organization for the construction of a luxury hotel and condo tower in Chicago.