Detectives of New South Wales (NSW) Police Force seized 13,353 cannabis plants and around 17.69 kg of dried cannabis, worth at least AUD16.9 million ($12 million), after searching several properties in Minimbah, Melinga and Moorland last Thursday and Friday.

Over the two days, police also arrested 14 Vietnamese men, aged 22 to 44, at the properties. They were either permanent residents, illegal migrants, or on student and bridging visas.

All were charged with the cultivation of prohibited plants in large commercial quantity, supplying prohibited drugs and contributing to criminal activity, according to NSW police.

Bail was refused to all suspects, expected to appear at Taree Local Court on January 19 next year.

The arrests and seizures were part of an ongoing investigation into a criminal syndicate behind the large-scale cultivation and supply of cannabis. The seizure was one of the most significant in Australian history, according to Drug and Firearms Squad Commander Detective Superintendent John Watson.

"Over the two days, 14 offenders were arrested, and more than 13,000 plants were seized with an estimated street value of over AUD40 million," Watson stated, as cited in a statement of the NSW police news website on Monday.

"As far as cannabis seizures go, we have not seen one of this size since the 1970s."

The investigation is ongoing.