Los Angeles police are investigating allegations by more than 50 women about possible sexual abuse by a University of Southern California gynecologist dating back decades, authorities said Tuesday.

Police said allegations against Dr. George Tyndall date from 1990 to 2016 during a period in which they estimate he could have treated over 10,000 women. They encouraged any other potential victims to come forward.

More than a dozen lawsuits have been filed against Tyndall and USC since the Los Angeles Times reported this month that women had complained about him for years and the university didn't take action until 2016. The scandal led to the resignation of USC President C.L. Max Nikias on Friday.

Tyndall, 71, has been accused of groping patients, conducting improper exams, taking photos of women's genitalia and making inappropriate racial and sexual comments. He denied wrongdoing in interviews with the Times, but has not returned messages from The Associated Press and it wasn't clear Tuesday if he had a lawyer who could comment.

A hotline established by the university had received more than 300 calls, but because some complaints are old they could be beyond the statute of limitations to bring charges that could include rape and other sexual assaults.

"Many of them are just inappropriate comments which, obviously, do not constitute a crime," Police Capt. Billy Hayes.

At least a dozen lawsuits have been filed so far. They allege Tyndall routinely made crude comments, took inappropriate photographs and forced plaintiffs to strip naked and groped them under the guise of medical treatment for his "sexual gratification."

USC has said Tyndall was placed on administrative leave in 2016 and never returned to treating students after officials received a complaint from a staff member at the health clinic. The staff member alleged that Tyndall made inappropriate comments to a patient in front of medical assistants.