A 31-year-old man was arrested on suspicion of smuggling around HK$84 million worth of gold by air, in what customs officers said was the biggest such case they had detected to date.

Customs officials on Monday said that based on intelligence and risk assessment, officers honed in on a freight consignment meant for Japan in late March.

The boxes were declared to be two air compressors, but x-rays found parts of the machines to have a very high density. Officers then found 146 kilos of gold inside.

Customs officials said the arrested suspect was a director of a company and they believed their operation helped smash a smuggling syndicate.

Investigations were ongoing and further arrests could be made.

Officers added that an estimated HK$8.4 million of tax could have been evaded had the shipment been made undetected.