WASHINGTON (Dow Jones/AP) — The Securities and Exchange Commission is calling on banks and insurance companies to inform investors about exposure to potentially troublesome loans and securities tied to riskier subprime borrowers.

Chief financial officers at about two dozen firms, including Wall Street investment banks, will get a written letter from the SEC on the matter, SEC Chairman Christopher Cox told reporters yesterday.

Potential losses or fallout from deteriorating credit markets, including subprime mortgage markets, prompted the SEC reminder.

The letter, expected to be sent yesterday, will go to companies that previously disclosed off-the-books investments in collateralised debt obligations, conduits and structured investment vehicles. While such investments aren't recorded on a company's balance sheet, SEC officials said information about them could be laid out for investors elsewhere.

Information that may be useful for investors would include ratings on off-balance sheet investments, including downgrades or write-downs; any difficulty in funding such investments; and the maximum losses to be borne by first loss note holders, the letter states. The SEC also wants companies to divulge any obligations to such investments, such as purchasing assets or providing liquidity, and how they stack up against other liquidity providers.

Known trends or uncertainties that could have a big effect on the company's operations, liquidity or capital resources also may need to be outlined to investors, according to the letter.