(Yoo Ah-in`s Instagram)

Actor Yoo Ah-in has been under investigation for illegal use of propofol, an anesthetic medication, according to police officials Thursday.

The Seoul Metropolitan Police Agency's drug investigation unit called in Yoo on Monday to question him about use of propofol for non-medical purposes, which constitutes a violation of the Narcotics Control Act, officials said.

Police has sent Yoo's hair samples to the National Forensic Service to secure evidence and placed an overseas travel ban on him.

His entertainment agency admitted Yoo has been under police investigation over propofol use.

"(Yoo) has been actively cooperating with police investigation and plans to address problematic issues," United Arts Agency said in a statement. (Yonhap)