A police raid on a factory in a small town in Wakayama Prefecture last month has uncovered a massive haul of cannabis with a street value estimated at ¥2 billion.

Police revealed on Wednesday they seized over 10,000 cannabis plants and arrested senior gang member Junichi Kimura, 54, along with three others, all from Osaka, on suspicion of possessing marijuana with intent to sell.

"I only dropped by for a visit," Kimura was quoted telling police.

According to police, about 11,000 plants in various stages of growth were discovered. Some 4,000 of them, worth about ¥2 billion, were fully grown and ready for distribution.

In the past several years, thousands of cannabis plants have been seized in Japan, but this was an extraordinary amount for a single raid, police statistics show.

On Oct. 26, police initially nabbed the four at the factory in the town of Katsuragi on suspicion of growing 24 cannabis plants and possessing about 340 grams of marijuana. Following the arrests, police combed the factory the same day and discovered the full extent of the operation.