Former Michigan State University President Lou Anna K. Simon was served with a subpoena by U.S. marshals today to compel her testify before a Congressional subcommittee about the Larry Nassar controversy, according to a spokesman for the committee.

Simon initially accepted an invitation to speak at a May 22 hearing of the U.S. Senate's Subcommittee on Consumer Protection, Product Safety, Insurance and Data Security, according to Frederick Hill, spokesman for the committee.

When that hearing was rescheduled for June 5, Simon's attorney told committee staff that she would not be available voluntarily on that date "or any date," Hill said.

Faced with that situation, Hill said, a subpoena was issued, which was given to Simon today in Traverse City by federal marshals.

Mayer Morganroth of Detroit, who is Simon's attorney, was not immediately available for comment.

Senators on the committee have said testimonies from MSU, USA Gymnastics and the U.S. Olympic Committee officials are "imperative" to their investigation into sexual abuse in amateur sports inspired by the Larry Nassar scandal.

Nassar worked at MSU for decades and was well known for his work with elite gymnasts before women began sharing their stories of sexual abuse, which he often did during medical appointments. He is currently serving a 60-year federal sentence on child pornography charges, and also pleaded guilty to several counts of criminal sexual conduct in Ingham and Eaton counties.

The Senate subcommittee hosted a hearing in April featuring testimony from Olympians Jordyn Wieber and Jamie Dantzcher - two of Nassar's most high-profile victims - and other former athletes impacted by sexual abuse in their sports.