A joint operation between American and Australian law enforcement led to the seizure of close to two tons of methamphetamine in California that was bound for the land down under, authorities announced late Thursday.

As part of their investigation, the Australian Federal Police and police in the southern state of Victoria arrested six people, including an American couple living in the Melbourne suburb of Woodstock. Police said they had found "[h]undreds of thousands of dollars of proceeds of crime" while executing a search warrant of the couple's property. They were not identified except as a 52-year-old man and a 46-year-old woman.

At a news conference in Melbourne, Australian Federal Police Assistant Commissioner Bruce Hill told reporters that the drug shipment intercepted last month was concealed in 850 electrical capacitors stored inside two large containers purported to contain audio equipment. The shipment also included 25 kilograms (55 pounds) of cocaine and five kilograms (11 pounds) of heroin. In all, the entire shipment was worth an estimated $1.3 billion.

Australian authorities said the seizure was the largest haul of methamphetamine ever recovered in the U.S., the equivalent of 17 million individual hits. Hill said the interception was carried out by agents from U.S. Customs and Border Protection, as well as Homeland Security Investigations Border Enforcement Security Task Force (HSI BEST) a branch of Immigration and Customs Enforcement.

"This historic seizure highlights just how important the U.S.-Australian partnership is in protecting Americans and Australians alike," acting U.S. Ambassador to Australia James Carouso said in a statement. "Every day, U.S. and Australian law enforcement officers work together to keep us all safe. My sincere thanks to these dedicated professionals."

Hill said that the quantity of drugs that were intercepted proved that Australia is being targeted by Mexican drug cartels.

"The Australian public who are consuming ice and other drugs are permitting organized crime to flourish," Hill said.

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The other four arrested suspects were identified as a 31-year-old man and a 29-year-old woman from another Melbourne suburb, Keilor Downs, where police recovered approximately 6.5 kilograms (14 pounds) of meth; a 31-year-old man from the Sydney suburb of Hinchinbrook, where police recovered approximately 2 kilograms (4.4 pounds of cocaine); and a 25-year-old man from another Sydney suburb, Bonnyrigg Heights.

Three of those arrested, including the American couple, were due to appear in a Melbourne court Friday on a charge of attempting to import controlled drugs. They face up to life in prison if convicted.