Throughout, the complaints allege a broad effort by the university to cover up the allegations and make sure they never seeped into the public eye. Although accusations of improper conduct against Dr. Tyndall dated back to the 1990s, he was allowed to continue working at the student health center until 2016. Then, after a complaint by a nurse, Dr. Tyndall was suspended. A year later, after an investigation, he was given a financial settlement and allowed to quietly retire. (Dr. Tyndall, 71, denied any improper conduct in interviews with The Los Angeles Times.)

In a letter issued on Friday and addressed to the university community, Mr. Nikias said the school was working with the Los Angeles Police Department, raising the possibility of criminal charges against Dr. Tyndall.

The university has faced criticism for not reporting Dr. Tyndall to the state medical board and for not notifying the broader university community about the misconduct.

“They allowed him to secretly retire in the hopes this would be put under the rug somewhere and no one would hear about it,” Ms. Masry said. “And that’s what backfired on them.”

The university’s senior leaders have said they did not learn of the allegations until 2017. Earlier complaints against Dr. Tyndall, which reportedly began in the 1990s, were dealt with by the health center’s director at the time, who did not raise them with the university’s administration and died in 2016.

Michael W. Quick, the university’s provost, flatly denied a cover-up in a letter on Monday to faculty and staff. He wrote, “I have seen media reports allege that the university leadership knew about Dr. Tyndall’s misbehavior for a long time, and that we covered it up for the sake of the USC brand. This is absolutely untrue. It is unthinkable. It is true that our system failed, but it is important that you know that this claim of a cover-up is patently false.”

The university has defended its handling of the matter, saying that top officials acted as soon as the allegations were brought to senior leaders at the school. The university has set up a hotline for students to report complaints of abuse, and has received hundreds of calls. In the wake of the revelations, the school has also fired two supervisors at the student health clinic where Dr. Tyndall worked.