SYDNEY, Australia -- Australian police arrested six people after what authorities said Friday was the largest single seizure of methamphetamine in the United States and the biggest drug haul bound for Australia.

U.S. Customs and Border Protection said 1,728 kilograms (3,800 pounds) of the drug were seized mid-January at the Los Angeles-Long Beach port complex along with smaller amounts of cocaine and heroin. The drugs were hidden in metal boxes labelled as loudspeakers. Australian authorities said it was also the largest haul of the drug intercepted while bound for Australia and would have provided around 17 million hits of the substance also known as ice.

Australian authorities said that the operation with the U.S. Department of Homeland Security, Drug Enforcement Agency, Australian Federal Police and Victoria state police had stopped "a tsunami of ice" from reaching their shores.

Police said that six people arrested in Australia on Thursday and Friday were tied to a U.S.-based syndicate under investigation over the drugs. Two of those arrested are Americans: a 52-year-old man and a 46-year-old woman. Police said the raid in the Melbourne suburb of Woodstock in which they were arrested also found "hundreds of thousands of dollars of proceeds of crime."

Police said that three of those arrested would appear in the Melbourne Magistrates Court on Friday, charged with attempting to import illegal drugs. Two other Australians face the same charge.

Australian Federal Police Assistant Commissioner Bruce Hill told a news conference in Melbourne that police now believe Mexican cartels are actively targeting Australia.

"They have been sending smaller amounts over the years. This is now flagging intent Australia is now being targeted," he said. "The cartel is among one of the most powerful and violent drug trafficking syndicates in the world."

None of the agencies involved has further identified the cartel.

The operation also involved raids in British Columbia on Thursday by the Royal Canadian Mounted Police, which resulted in the seizure of "a significant quantity" of suspected proceeds of crime, police said.

Jason Halls, Victoria manager for the Australian Criminal Intelligence Commission, said the drugs would have had an "immeasurable" impact on the Australian community. He said sewage drug monitoring data showed Victoria state -- which has a population of 6.3 million -- was estimated to consume just over 2 tons of ice each year.

The previous record haul of meth seized in Australia was 1.3 tons in December 2017.

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Associated Press writer Robert Jablon in Los Angeles contributed to this report.