Hong Kong customs officials said Thursday they have seized elephants tusks valued at more than $9 million US in ivory this week in the city's biggest ivory trade bust in 30 years.

Customs officers discovered 7,200 kilograms of elephant tusks on Tuesday in a shipment from Malaysia that had been labelled as frozen fish, the Customs and Excise Department said.

INTERACTIVE | Elephants for sale

Customs officers displayed samples of the tusks piled on the floor at their offices close to some of Hong Kong's giant container ports.

A customs officer stands guard next to seized elephant tusks during a news conference at the Kwai Chung Customhouse Cargo Examination Compound in Hong Kong on Thursday. (Anthony Wallace/AFP/Getty Images)

The department said three people at a trading company in Hong Kong have been arrested in connection with the shipment.

Hong Kong, a major transshipment hub for illicit wildlife products, is preparing to ban local ivory sales by 2021.

But under Hong Kong's customs regulations, anyone found importing or exporting endangered species without a licence or trying to smuggle such items into or out of the territory faces possible fines and imprisonment.