In 2010, Jo joined Cheongju University's drama department but after the allegations of raping and harassing students surfaced last month, he was sacked.
Jo initially denied the claims against him, but later issued a statement accepting that he had acted improperly.
An's aide, who accused him of sexual misconduct in a television interview, filed a complaint with prosecutors this week, her lawyer's office said earlier.
The police did not give many details regarding the case, but several key media outlets report the actor is believed to have committed suicide. Min-ki was accused of abusing eight of his students.
The police suspect it might be a suicide, according to Yonhap News.
When he was confronted with evidence that included lewd text messages he had sent, he admitted his behavior, apologized and promised to cooperate with police.
"First of all, I offer my words of apology to the people and the provincial residents", Ahn said outside the prosecutors' office, as a barrage of flashbulbs went off.
In the arts, the most high-profile figures to be accused are award-winning film director Kim Ki-duk and poet Ko Un.
"If this action takes effect, it would inevitably deal a serious blow to South Korea's steel exports to the United States".