Officers believed the mansion in Sai Kung had been used as a drug factory, where traces of drug-making activities were found within the mansion.

A Customs spokesman said the premise was located after receiving intelligence.

Officers intercepted a 25-year-old man in Sai Kung at around 6pm on Monday, finding about 2.2kg of suspected crack cocaine on the suspect.

“Officers later escorted the suspect to a mansion within the district and seized 52kg of suspected cocaine and about 620g of suspected crack cocaine from a safe within the premises,” the spokesman said, “the haul had an estimated street value of nearly HK$73 million.”

“We believe the suspect was specially trained in manufacturing drugs, making use of rare chemicals to whitened the drugs to increase the selling price.”

The spokesman also added that the drugs were packed in packages labeled with automobile brands.

The suspect, who claims to be a construction worker, was arrested on suspicion of manufacturing and trafficking in a dangerous drug. He will be brought to the Kwun Tong Magistrates' Courts tomorrow.