Police have identified two suspects believed to be behind a blackmail scheme that involved distributing drinks laced with drugs to high school students in Seoul's Gangnam area.

According to the police on Monday, the narcotics crimes investigation unit under the Seoul Police Agency specified a South Korean national surnamed Lee and a Chinese citizen surnamed Park as part of the “upper echelons” of the criminal case, leaving open the possibility that there could be a more senior mastermind.

Lee, in his 20s, was previously implicated in a voice phishing scheme in South Korea and has reportedly been in China since October.

The police filed for arrest warrants with a local court while calling for cooperation from Chinese police authorities.

Police officials suspect the two ordered their accomplices in South Korea to concoct beverages containing methamphetamine and distribute the products in Seoul. One of the accomplices, surnamed Gil, was arrested in Wonju, Gangwon Province last Friday.

Earlier, several other suspects in the case were also apprehended in Seoul and Daegu on suspicions that they tricked students into drinking the beverage in Seoul’s Gangnam area, known for its private academies, by claiming that it helps improve memory.

The suspects worked in pairs near two subway stations, saying it was a tasting event and asking the students for their parents' contact information, who the group then allegedly blackmailed by threatening to report the children to the police and school for using drugs.