Bond giant Pacific Investment Management said on Monday that it could be sued by the country’s top securities regulator over how it valued assets in one of its most popular funds aimed at small investors.

The Pimco Total Return Active ETF, an exchange-traded fund previously managed by star investor Bill Gross, has been under investigation by the Securities and Exchange Commission for at least a year for allegedly artificially boosting returns from its trading of certain mortgage bonds, The Wall Street Journal first reported in September 2014.