Magic mushrooms, marijuana candy and LSD stamps were among a haul of drugs worth around HK$12 million seized in Yau Tong last week, police said on Sunday.

Officers said they raided a factory building in the area on April 19 and another the following day, after discovering that the sites were being used for manufacturing and trafficking dangerous drugs destined to be sold in Hong Kong.

A 25-year-old man was arrested.

"During the operation, our officers seized drugs with a total market value of more than 12 million dollars, including 12.5 kilogrammes of heroin, 8 kilogrammes of marijuana flowers, 270 sticks of marijuana vape juice, 500 millilitres of marijuana oil, marijuana candy and cookies, magic mushrooms and LSD stamps," said Senior Inspector Matthew Fung.

"Our officers also examined tools found in one of the units suspected to be used for manufacturing and packaging the drugs. We believe that this operation has successfully cut off the supply chain of this drug trafficking group."

Fung said officers were trying to trace the source of the raw materials used to produce the drugs found.