The Michigan State University dean who supervised disgraced gymnastics doctor Larry Nassar was arrested Monday on unknown charges, weeks after the school announced plans to fire him over his "personal conduct."

William Strampel was taken into custody on the eve of a press conference by the state attorney general's office, which has been conducting a wide-ranging investigation into MSU's handling of sexual-abuse allegations against Nassar.

An inmate database confirmed that Strampel, 70, was being held at the Ingham County Jail, but no charges were listed. The AG's office declined comment, as did MSU, and an attorney who represents Strampel in civil matters did not immediately respond to a request for comment.

Strampel was the longtime head of the College of Osteopathic Medicine, where Nassar had his sports medicine practice until he was unmasked as a serial predator who molested more than 200 patients, including Olympic champions, under the guise of exams and treatments.

The dean came under fire amid revelations that he failed to ensure Nassar was following precautions put in place after Nassar was accused in 2014 of molesting patients and cleared by a flawed internal investigation.

Earlier this year, as the campus was rocked by the scandal, Strampel stepped down from his managerial position at the college. MSU's new interim president then announced he was moving to revoke Strampel's tenure, which would allow him to be terminated.

"William Strampel did not act with the level of professionalism we expect from individuals who hold senior leadership positions, particularly in a position that involves student and patient safety," said John Engler last month.

"Further, allegations have arisen that question whether his personal conduct over a long period of time met MSU's standards. We are sending an unmistakable message today that we will remove employees who do not treat students, faculty, staff, or anyone else in our community in an appropriate manner."

A former Michigan State University dean who supervised Larry Nassar is under arrest. Mark Cunningham / Getty Images

The school declined to comment further, but last week the Wall Street Journal reported that in the falls of 2016 Strampel told a group of students and staff that he did not believe Nassar's accusers and that he didn't want to fire him.

Those comments presumably would not lead to criminal charges, however, so it's unclear what the AG's office has uncovered in its own investigation.

John Manly, an attorney who represents many of Nassar's victims, said in a statement that his clients were "encouraged" by Attorney General Bill Schuette's action.

"It demonstrates that he is serious about investigating the systemic misconduct at MSU that led to the largest child sex abuse scandal in history and holding the responsible parties accountable," Manly said.

MSU has been accused of mishandling reports of Nassar's abuse stretching back 20 years and faces a growing mountain of lawsuits and probes by the NCAA and the Department of Education.

Nassar, meanwhile, is in federal prison, serving the first of three sentences that will keep him locked up for the rest of his life.