Federal prosecutors investigating Mark Walter's insurance businesses requested records from credit rating firm Egan-Jones as part of their probe into the billionaire's investment practices.

According to Bloomberg Markets, Walter's insurance companies frequently invested in bonds that carried Egan-Jones ratings, with the firm providing the only known ratings for over 20% of those assets, based on industry records.

The Department of Justice's request for Egan-Jones' records suggests investigators are examining the relationship between Walter's insurance entities and the rating agency, potentially focusing on how these bond investments were evaluated and whether proper due diligence was conducted.

This development adds another layer to the ongoing legal scrutiny facing Walter, founder of Gateway and former chairman of Guggenheim Partners, whose business dealings have attracted increased regulatory attention in recent months.