(Bloomberg) — The U.S. regulatory probe into Bill Gross's Pimco Total Return ETF is separate from a broader scrutiny of disclosure in the exchange-traded fund industry, according to a person familiar with the matter.

The U.S. Securities and Exchange Commission is investigating whether Pacific Investment Management Co. bought smaller lots of bonds at discounts, then marked them up, according to the person, who asked not to be identified because the probe isn't public. While the SEC is probing disclosure issues surrounding ETFs industrywide, the Pimco case is different from that investigation, the person said.

The Pimco Total Return ETF produced more than twice the return of Gross's similarly managed mutual fund in the first three months after it was started in March 2012, helping it attract assets faster than any other actively managed ETF. The probe is the latest hurdle faced this year by Pimco, which is dealing with record redemptions at its main mutual fund and negative publicity stemming from the abrupt departure of its former chief executive officer, which was followed by the biggest management overhaul in its history.