The Customs Department said on Saturday that it had seized suspected cocaine with an estimated market value of about HK$110 million, and arrested two teenagers and a woman.
Vincent Lee, who heads the department's drug investigation group, said they became suspicious after X-raying an electric transformer shipped in from Costa Rica last month.
Authorities then disassembled the oil-filled object to find around 120kg of suspected cocaine inside metal compartments, before restoring the "transformer" for the delivery company to give it to the alleged drug syndicate.
Officers said the syndicate had changed the storage location several times, and it wasn't until around 20 days later that two teenage boys signed for the item in rural San Tin.
The pair, aged 14 and 15, were arrested on Thursday and have been charged over attempted drug trafficking. They will appear at the Fanling court on Monday.
A 49-year-old woman who said she worked for a logistics company was also arrested on Friday.
Lee said the pandemic has changed the way drug syndicates transport their goods, saying they now tend to transport drugs in bulk by sea or air due to travel restrictions.