Six men were arrested Wednesday in connection to the 2016 seizure of 185 kilograms of hallucinogenic kiken (dangerous) drugs from an apartment in Tokyo, investigators said.

Police and the health ministry's narcotics control department said they raided the apartment and seized the drugs on June 8, 2016 — marking one of the largest confiscations of its kind in the country. The street value of the haul was estimated at ¥3.6 billion ($33 million).

Kiken drugs refer to those containing chemical agents that cause hallucinations and produce effects similar to illegal narcotics. The government banned the possession and use of such drugs in 2014.

Katsumi Yoneya, 35, and the five others allegedly smuggled raw materials from overseas to produce the drugs and sold them online, the police said.

The apartment was rented under Yoneya's name. The police raided the apartment on a tip-off from the owner who thought it was being used as a warehouse, according to investigators.