MELBOURNE, Victoria, Australia - Three people have been charged in relation to Australia's largest ever onshore methamphetamine seizure, worth more than $1.2 billion dollars.

The development comes after Australian Federal Police (AFP) executed a series of search warrants across several Melbourne properties.

The three charged faced the Melbourne Magistrates' Court on Thursday

The AFP alleges two men (aged 37 and 38) and a woman (aged 37) were involved in the importation of more than 1.6 tonnes of illicit drugs equal to almost 16 million drug deals in stereo speakers originating from Bangkok, Thailand.

In total, 1.596 tonnes of methamphetamine and 37 kilograms of heroin (a total of 1633 kgs) were detected with an estimated street value of $1.197b and $18.5m respectively.

In addition, this is the largest seizure of heroin in Australia since 2017.

The AFP executed search warrants at properties in the Melbourne suburbs of Darley, Sunshine West, Brooklyn, Elwood and Murrumbeena throughout the day on Wednesday.

Australian Border Force (ABF) officers detected the huge haul in vacuum-sealed packages concealed within the speakers during a sea cargo inspection at the Melbourne Container Examination Facility in April, this year.

The three accused are facing charges for which the maximum penalty is life imprisonment.

"It will be alleged that two of the three suspects charged are trusted industry insiders, and that this joint operation has identified and removed serious vulnerabilities from the Melbourne waterfront and we could not have done this without the support and assistance of the public," AFP Deputy Commissioner Neil Gaughan said Thursday.

"In addition, under Taskforce Storm joint arrangements, the AFP has shared intelligence with Thai authorities on this matter in accordance with relevant guidelines, resulting in them conducting their own investigation, which is currently ongoing."

Deputy Commissioner Gaughan said that these charges are extremely serious.

"Australia is a lucrative market for drug traffickers only due to the amount of drugs consumed by the public and the price paid for those drugs. This is a social problem that is the responsibility of everyone to address," he said.

"Police will continue to protect our communities and borders against exploitation by sophisticated criminal networks, but it is the responsibility of everyone to educate and support each other to stop the high use of drugs we see in Australian society."

ABF Assistant Commissioner Enforcement Command Sharon Huey said ABF officers work tirelessly every day to stop illicit narcotics from reaching the Australian community and causing harm, and this seizure was another example of their skills, intuition and diligence.

"Our officers are constantly alert to attempts to conceal illicit substances, no matter how creative criminal syndicates are in trying to hide them," Assistant Commissioner Huey said.

"In this case officers using x-ray technology detected anomalies inside the speakers, with the subsequent deconstruction of one allegedly revealing a number of vacuum sealed packages inside."

"This is another example of the ABF and AFP working together to disrupt the criminal networks that seek to profit from the misery of others and to bring those responsible to account," Huey added.