Two Australian customs agents and an IT worker have been charged in connection with the country's largest seizure of methamphetamine, which had been smuggled to Melbourne from Bangkok in stereo speakers.

The drug – also known as ice and crystal meth – weighed the equivalent of 1.7 U.S. tons and had a street value of $818 million, by some police estimates. Authorities also seized about 82 pounds of heroin, the largest haul of that drug in Australia since 2017, police said.

Federal Police Deputy Commissioner Neil Gaughan told reporters the crystal meth seized was nearly “a quarter of the annual usage in Australia, so this will have an impact.”

Married customs agents Rachel Cachia, 37, and Donovan Rodrigues, 38, appeared in the Melbourne Magistrates Court Thursday with co-accused Stephen Mizzi, 37, on drug importation charges that carry potential life prison sentences.

They did not enter pleas or apply for bail. They will remain in custody until they appear in court next on May 7.

Customs agents in Australia are private-sector employees who facilitate cargo movements through ports. They do not have security clearance at ports but operate as independent import-export experts.

Gaughan accused the couple of being "middle-to-high up" in the drug trafficking operation.

"They are trusted insiders in the industry. They used their position of trust to circumvent the border controls that exist within Australia," Gaughan said. "This vulnerability has been fully removed."

He said police were now working to bring the bosses of the operation to justice.

COAST GUARD SEIZES $92M WORTH OF COCAINE

Cachia, Rodrigues, and Mizzi were arrested after police executed search warrants on Wednesday at several Melbourne properties.

Australian Border Force officers detected the haul in vacuum-sealed packages concealed in speakers at the Melbourne waterfront in April.

The drug shipment came to Australia from Thailand, but Australian authorities suspect it originated from another Southeast Asian country, which they did not name.

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Australia is an attractive market for international drug traffickers because of the relatively high prices that Australian drug users are willing to pay.

The Associated Press contributed to this report.