The granddaughter of late textiles tycoon Law Ting-pong, 29-year-old Queenie Rosita Law, was held for at least three days last month before family members paid a ransom of HK dollar 28 million for her to be released.
Police in Hong Kong had embarked on a massive operation to hunt down the suspected kidnappers, deploying hundreds of heavily armed officers, helicopters and marine vessels, and setting up roadblocks.
Hong Kong police said earlier that another suspect was arrested at a border checkpoint in Hong Kong as he attempted to flee to the mainland.
Police seized more than HK dollars 2.8 million (about USD 361,000) in cash - or 10 per cent of the ransom the kidnappers had obtained - and property including watches and jewellery, according to the latest statement.
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A series of high-profile kidnapping cases shocked Hong Kong in the 1990s.
The eldest son of the city's richest man Li Ka-shing was kidnapped in 1996 by the infamous crime boss Cheung Tze-keung, nicknamed "Big Spender", who also kidnapped property tycoon Walter Kwok in 1997.
Cheung fled to China but was later arrested by mainland authorities. He was executed in 1998.