The concrete tunnel, equipped with lights, vents, steel reinforcements and even rails, started under a garage near the Chinese city of Shenzhen and stretched for 40 metres under a river and into a village in Hong Kong, a state-run news website reported.
Authorities believe gangs intended to use it to send mobile phones and electronic goods to Hong Kong. Semi-autonomous Hong Kong has different tariffs from the mainland, and smugglers could make huge profits by avoiding border fees and taxes, the reports said.
Officials described the tunnel as a professional job, estimated to have cost almost USD 500,000 to build. The tunnel was about 20 metres short of its intended destination, a village on the Hong Kong side of the frontier.
The tunnel stood about 0.8 metres wide and 1 metre high, just big enough for an adult to crawl through.
The authorities destroyed the tunnel yesterday and a man has been arrested.