Four Korean-Americans, including one former gang member with a violent criminal history in the U.S., were arrested by police on Wednesday on suspicion of falsifying their academic credentials.

According to the Seoul Metropolitan Police Agency on Thursday, five were arrested after being caught smoking marijuana together, and further investigation found that one was wanted for drug trafficking.

All of the arrested were found to be teaching English in the capital, including in Gangnam-gu, an area priding itself in its academic facilities, and four were found to have forged university diplomas, police said.

According to police, two had served seven-year sentences, one, surnamed Kim, for second-degree murder and another for kidnapping and rape.

Kim, an overseas adoptee, was a gang member in Arizona and came to Korea in 2008 after serving his sentence. He taught at a private academy after procuring a forged diploma from Arizona State University online, police found.

One of the arrested was a public service worker, surnamed Lee, who expatriated to Korea after being sentenced to two-years in prison for possession of narcotics and firearms, according to the police report.

Police have also reported four other individuals, including a private academy owner, to the Education Ministry for failing to make proper background checks.

On Aug. 8, a 33-year-old Korean-American, surnamed Kim, wanted for two counts of attempted murder in the U.S., was captured in Seoul after running an English-language academy under a false identity.

Kim is suspected of shooting at two members of a Mexican gang in 1997, but fled to Korea the same year.

He assumed an identity, forged a University of California, Los Angeles diploma, taught at numerous hagwon, and eventually opened an SAT hagwon in Gangnam, charging students a minimum of 1 million won a month.

The arrest in August prompted ministry officials to conduct a thorough investigation of private academies in the Gangnam district, but the recent arrests calls the effectiveness of those efforts into question.

By Robert Lee (robert@heraldcorp.com)