Thirty-seven people, many of them foreigners staying in South Korea as English teachers, have been arrested and booked on charges of smuggling, trading and taking marijuana, police said Wednesday.

Those arrested included a South Korean national with U.S. residence, surnamed Shin, as well as a Korean American, surnamed Kim, according to the Seoul Metropolitan Police Agency. Both were working as English teachers.

They brought 2 kilograms of hemp into South Korea earlier this year through the U.S. military mail service and sold them to 32 drug buyers through South Korean and Nigerian drug dealers for the profit of around 110 million won (US$107,716).

The two drug dealders were also among those arrested.

The police said the drug buyers, booked for smoking the illegal drug, were mostly foreigners who are teaching English language at local colleges, elementary schools, private institutions or even kindergartens mainly in areas near Seoul.

"Shin and his group mostly dealt with foreigners, given that if they are (caught and) convicted of drug related charges, they could be punished and kicked out of their jobs," the police said. "They sold the hemp to English native teachers whom they met at a foreigner-only club located in Suwon," a city 45 kilometers south of Seoul.

The police investigation showed that the arrested Nigerian drug dealer has taught English at a kindergarten in Yongin near Suwon while he was under the influence of marijuana.

An American English teacher, who was among those arrested, shaved all his hair to evade a drug test, but he was tested positive in a urine examination, the police said.

Police plans to tighten crackdown on drug crimes involving foreign teachers.

Under South Korean law, marijuana users can be sentenced to a maximum of five years in jail or fined up to 50 million won. (Yonhap)