Lee Sun-kyun, known for his role in Oscar-winning movie “Parasite,” could be summoned for questioning sometime this week, reports said Sunday, citing police, as part of an expanding investigation into suspected drug use involving the actor and seven others.

According to the reports, police are also considering a warrant to take a hair sample from the 48-year-old for drug testing in case he refuses to comply. The police probe is still at an internal stage, a precursor to a formal criminal investigation, and the police are assessing whether to follow up on allegations of his involvement in illegal drug use this year.

Lee is reported to have used unspecified illicit substances at escort bars and residential areas in southern Seoul’s Gangnam area on several occasions this year, according to reports.

Lee is one of eight people subject to the investigation. The others include Han Seo-hee, a K-pop trainee who came to public attention in 2017 for smoking cannabis with former Big Bang bandmate T.O.P at his apartment, and Hwang Ha-na, the granddaughter of the founder of Namyang Dairy Products. The two are also suspected of using drugs at adult entertainment facilities linked to the actor, according to reports. The names of others have not yet been revealed.

Lee’s case is one of several signs that South Korea is struggling to tackle illegal drug use, despite a recent drive to regain its “drug-free” reputation.

Apart from Lee’s drug case, prosecutors on Thursday indicted actor Yoo Ah-in -- known recently for Netflix series “Hellbound” -- without detention on charges of habitual illegal drug use, nearly a month after the court rejected an arrest warrant for him for a second time.

The 37-year-old actor, who was born Uhm Hong-sick, is suspected of breaching the country’s Narcotics Control Act by misusing propofol -- a substance used to help relax or sleep before and during surgery or other medical procedures -- and other medical drugs on 181 occasions at clinics across Seoul since 2020.

While the fallout continues over drug use allegations against A-list actors, the drug crime investigation unit at the Seoul Metropolitan Police Agency on Friday said they had arrested 37 people for drug offenses in a recent bust, including a smuggler, eight distributors and 28 purchasers. Police have requested a red notice for the purported mastermind of the operation, who is believed to be staying overseas.

Police seized 9 kilograms of methamphetamine during the investigation.

Health Ministry data reviewed by the Board of Audit and Inspection on Thursday showed that some 44 doctors had prescribed narcotics for themselves over 50 times a year from May of 2018 to the end of last year, raising concerns about loopholes in attaining drugs through self-medication and the ministry’s lack of safeguards over prescriptions.

In addition, authorities detected a stark rise in illegal foreign exchange transactions over the past five years, with some money laundering methods used for illicit drug purchases and smuggling, according to customs data received by Rep. Hwang Hee of the main opposition Democratic Party of Korea.

Meanwhile, some 12,700 drug offenders were arrested in the first eight months of 2023, with a particular increase in younger age groups, far surpassing last year’s total of 12,387 arrests, which was the highest number in 10 years, according to the National Police Agency.