Three people in Melbourne have been arrested and charged in connection to Australia's biggest ice bust in history.

More than $1billion worth of methamphetamine was seized after border agents discovered the drugs hidden in a cargo shipment in Victoria in April.

Two men and one woman, all aged in their 30s, were arrested on Wednesday after search warrants were carried out at homes across the city.

Two of three suspects have been alleged to be customs agents, according to Australian Federal Police.

'They are trusted insiders within the industry. They used their position of trust to circumvent the border controls within Australia,' Commissioner Neil Gaughan said.

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More than $1billion worth of methamphetamine has been seized after the drugs were discovered hidden in a cargo shipment in Victoria

The massive bust marks the biggest ever onshore seizure of the drug in Australia

The haul is the biggest ever onshore seizure of the drug in Australia, with more than 1.6 tonnes of ice recovered, in addition to 37kg of heroin, the largest bust since 2017.

Border Force officers detected the drugs hidden in speakers sent from Bangkok, Thailand.

Officers picked the cargo shipment for further inspection in a targeting operation and, after being x-rayed at Melbourne Container Examination Facility, they noticed anomalies in the speakers.

They then took the speakers apart and found vacuum-sealed bags of the drug inside.

ABF Regional Commander Victoria Craig Palmer said the record detection - equivalent to 16 million drug deals - would have a significant impact on drug supply.

In the same month, four men were arrested in Sydney after Australian Border Force discovered half a tonne of ice worth almost $400million in a clothing container.

Two men and one woman, all aged in their 30s, were arrested on Wednesday after search warrants were carried out at homes across the city

Border Force officers detected the drugs hidden in speakers sent from Bangkok, Thailand

Investigators found six of the 10 pallets contained 500 packages of a white crystalline substance, which was confirmed to be methylamphetamine.

The drugs, which tipped the scales at 500 kilograms, have an estimated potential street value of $375million.

One of the men arrested was found sitting a massage chair at a Westfield shopping centre in Hurstville, southern Sydney.

The drugs were seized as part of an ongoing investigation where police have also recovered $200,000.

Amid the investigation, police arrested a 35-year-old man as he walked down the street in Wolli Creek, Sydney's south, on Thursday about 12pm.

A 55-year-old Canadian National was then arrested at a shopping centre in Hurstville.

In a separate incident earlier this year Australian police arrested six people in Victoria and New South Wales after a huge shipment of ice was found in California.

The 1.7 tonne haul, also understood to have been concealed in audio equipment, was bound for Australia.

The drug bust was the result of a joint U.S. and Australian investigation.