A Securities and Exchange Commission probe of commercial loans belonging to Fifth Third Bank (FITB) is doing little to assuage any fears of a shaky commercial real estate market. The SEC subpoenaed accounting and reporting records on commercial loans belonging to the banking platform this week, according to SEC regulatory filings. While Fifth Third Bank did not reveal the exact nature of the inquiry, the company's Chief Financial Officer Daniel Poston is quoted by the Wall Street Journal as saying the nature of the investigation remains unclear. The bank, which operates residential mortgage unit Fifth Third Mortgage Co., saw its stock price decline more than 4% in Tuesday afternoon trading. The investigation comes at a time when analysts are unsure about the fate of commercial loans. Analytics firm Trepp released a report Tuesday saying commercial loans littered the balance sheets of 12 U.S. banks that failed in February. In fact, commercial loans made up a majority of the banks' nonperforming loans. However, these loans are generally localized to three states: California, Georgia and Florida. Nonetheless, reports showing an uptick in the commercial real estate and related structured finance markets tend to be in big cities in New England or along the East or West Coast "gateway" locales. Fifth Third is a regional bank based in Cincinnati. Write to Kerri Panchuk.