Police say they have seized 34 kilogrammes of heroin with a street value of around HK$25 million from a flat in Sha Tin.
Officers said on Monday that they believe the heroin was transported to Hong Kong from Southeast Asia in capsule form and was then pressed into bricks.
Two men, aged 24 and 26, were arrested on Saturday on Wang Pok Street.
Senior inspector Cheung Chun-long said a gang went to some lengths to try to stop the authorities from detecting their drug smuggling.
"After they imported the drugs arriving in Hong Kong, they arranged somebody to take out the powdered heroin from the capsules and then used a hydraulic jack to transform it into brick form," Cheung said.
The two men arrested were charged with manufacturing dangerous drugs and were to appear at Shatin Magistrates' Court.