Harrisburg lawyer Claudia Williams, a former member of an advisory committee to The Second Mile, said Friday she was interviewed by an agency official. She says he told her the probe is focused on whether the charity solicited donations by mail.
The Associated Press left messages with the U.S. Postal Inspection Service.
The Patriot-News in Harrisburg was the first to report the investigation.
Multiple investigations are under way following allegations that Sandusky engaged in sexual misconduct involving 10 boys over 15 years. Prosecutors say he found his victims through The Second Mile.
The 68-year-old Sandusky denies the allegations and remains confined to his home while awaiting trial.
Information from: The Patriot-News, http://www.pennlive.com/patriotnews