An investigator shows one of the shoes used for smuggling illicit drugs into Korea from Cambodia, at the Incheon District Prosecutors' Office in Incheon, Tuesday. Newsis

Sixteen members of four different criminal organizations have been indicted on charges of smuggling illicit drugs worth 7 billion won ($5 million) into Korea from Cambodia.

The Incheon District Prosecutors' Office said Tuesday that the suspects will stand trial on charges of smuggling 21.3 kilograms of methamphetamine, 1.5kg of ketamine and 2.3kg of synthetic cannabinoids through Incheon International Airport between December 2023 and June.

The prosecution said it is also searching for three other accomplices overseas in cooperation with Interpol.

A 23-year-old man who played a key role in the inter-country operation before his arrest in Vietnam was found to have recruited smugglers on Telegram, an instant messaging app. He offered each smuggler cryptocurrencies valued at 10 million won per trip.

About a dozen people joined him, including four teenagers. As directed, they concealed the drugs inside their shoes and waist bags and successfully passed the screening undetected.

Even more drugs would have been smuggled into the country if one of the members had not reported the operation to the police. The man reportedly turned himself in after being spooked by the order to bury the drugs on a mountain.