A Korean man has been taken into police custody for growing marijuana plants on the rooftop of a building in downtown Seoul, police said Thursday.

The 45-year-old suspect is accused of cultivating 18 marijuana plants worth approximately 27 million won ($25,200), for four months from August 2013. Police found them in a greenhouse on the rooftop of a six-story commercial building in central Seoul, which had been converted into a marijuana farm.

The greenhouse was equipped with ventilation, lighting and heating systems to create the ideal environment for growing the plants, according to the Seoul Metropolitan Police Agency. The facilities led to monthly power bills of 1.6 million won, the officials said.

“Lee set up a triple-layer door at his greenhouse to avoid a police clampdown. The suspect appeared to have made detailed plans such as using an English alias and communicating with his clients using only phones bought under false names,” the SMPA officials said.

According to police, the suspect received 20 marijuana seeds through international shipping from Canada in December 2013.

Police said he learned how to grow marijuana in California, where he grew up, and was deported from the U.S. after serving 10 years in jail for drug trafficking.

The SMPA said it also booked two more people for allegedly buying the marijuana from Lee and trading them locally.

By Suk Gee-hyun (monicasuk@heraldcorp.com)