Australia has made its largest cocaine haul ever after seizing a yacht carrying 1.4 tonnes of the drug with an estimated street value of Aus$312 million (US$239 million).

The boat was stopped off the New South Wales coast on February 2 and six men were arrested, police said Monday, following a two-and-a-half year joint investigation between Australia and New Zealand.

“This is the largest cocaine haul ever seized in a single operation in Australia’s history,” said Immigration Minister Peter Dutton.

Police allege the yacht sailed from New Zealand to a “mothership” in the South Pacific to pick up the drugs last month.

A 63-year-old New Zealand man and a 54-year-old Swiss-Fijian dual national who were aboard the yacht were taken into custody, while four men aged between 32 and 66 were arrested in Sydney.

The haul is the second record-breaking bust in recent weeks, with police dismantling a cocaine ring in December in a joint operation with Tahiti.

That was previously the largest haul of its kind, with the sting netting 1.1 tonnes of the drug in Tahiti and Sydney worth hundreds of millions of dollars, all destined for Australia.

With high street prices making Australia an attractive destination for drug-smugglers, police say they have stopped more than 11 tonnes of illicit substances bound for the local market in the past 18 months.

“We hope that this operation sends a strong message to anyone thinking of smuggling drugs: no matter how innovative or complex their ways are, our evolving detection methods and resources, including at sea, will keep up with them,” said Australian Federal Police deputy commissioner of operations Michael Outram.