Hong Kong and Shenzhen law enforcement agencies have smashed a cross-boundary smuggling syndicate arresting 12 people, including the mastermind, and seizing $8.4-million worth of goods.

The syndicate used a self-made 600-metre long underground conduit across Shenzhen River to smuggle goods to the Mainland, the first of its kind to have been detected.

Shenzhen Public Security Bureau Border Defence officers searched a site near the boundary suspected to be the operating point of the conduit on July 4. A large quantity of mobile phones, mobile phone LCD displays and computer RAM chips worth about $1.2 million were seized with five men arrested.

Customs officers raided the smuggling operation site in Hong Kong inside a fenced-off area on Lin Ma Hang Road, Ta Kwu Ling, and searched the syndicate's warehouses in Ping Che and Kwun Tong leading to a seizure of $7.2 million-worth of goods, including mobile phones, motherboards and LCD displays of mobile phones and computer harddisks.

Five men and two women were arrested including two two-way permit holders and a Hong Kong man suspected to be the mastermind.