The bank loans under scrutiny, the total of which has not been previously reported, came from two financial institutions in the New York region that have catered to the taxi industry, Sterling National Bank and the Melrose Credit Union, according to business records and people with knowledge of the matter, including a banker who reviewed the transactions.

Federal investigators in New York are seeking to determine whether Mr. Cohen misrepresented the value of his assets to obtain the loans, which exceed $20 million.

They are also examining how he handled the income from his taxi medallions and whether he failed to report it to the Internal Revenue Service.