Federal prosecutors for Pennsylvania's Middle District could not immediately be reached for comment Thursday night.
But their entrance into the case marks only the latest inquiry opened since Sandusky's arrest on sex-abuse charges.
In November, a state grand jury alleged that Sandusky molested at least 10 boys that he met over a 15-year period through the Second Mile, a charity for underprivileged children he founded in 1977. Some of those assaults purportedly occurred on Penn State football trips and at the university's athletic facilities.
Curley and Schultz were also charged with lying under oath about their knowledge of a 2002 incident that allegedly occurred in the football locker-room showers.
All three men have maintained their innocence and have pleaded not guilty.
But the months since have left the university bruised from the fallout. Penn State's board of trustees accepted Spanier's resignation and fired longtime football coach Joe Paterno for their failure to report purported knowledge of Sandusky's actions to outside authorities. And the school has since become the subject of about a half-dozen administrative investigations.
In November, trustees appointed former FBI Director Louis J. Freeh to lead the university's internal inquiry. The U.S. Department of Education, state legislators, and the NCAA have also opened probes into how Penn State and its athletic department handled the allegations.
According to the Sandusky grand jury's 23-page report, the former coach took at least two of his victims to Penn State bowl games in San Antonio, Texas, and Tampa, Fla.
Police in both cities have opened their own investigations into the assaults that allegedly occurred on those trips.
And while the nature of the U.S. Attorney's Office subpoenas remains unclear, federal authorities are often called in to investigate crimes that occur across state lines.
Sandusky's former charity, the Second Mile, has also come under review in the scandals' wake. Second Mile chief executive officer David Woodle has said the organization received and complied with federal subpoenas in November for Sandusky's travel records. He did not respond to requests for comment Thursday night.
So far, Sandusky's attorney, Joseph Amendola, said that federal prosecutors had not approached him or his client.
Sandusky is set for trial on state charges in May.
Contact staff writer Jeremy Roebuck at 267-564-5218, firstname.lastname@example.org,
or @jeremyrroebuck on Twitter.