The raids on Thursday and Friday, part of a massive operation involving Griffith Police and the State Crime Command, took the week's haul to more than 10,000 plants with a street value of over $20 million.

In one bust alone on Friday, police unearthed more than 5000 plants - valued at about $10 million - on a Nericon property.

In two other raids, teams of workers were "panic harvesting" crops when police arrived.

All up, 11 properties were raided with 18 people arrested so far in what marks the biggest marijuana seizure in Griffith in more than a decade.

Drug Squad commander Detective Superintendent Nick Bingham said police had identified a number of offenders linked to high-level organised crime and drug syndicates.

"A large number of those arrested ... were farmhands employed to cultivate and harvest plantations," Det Supt Bingham said.

"(But) we have also identified a number of others allegedly linked to Italian organised crime syndicates and investigations will continue into these syndicates.

"I can assure the community that we will make further arrests and we will continue to uncover and eradicate cannabis crops."

He said the plants were mainly destined for the capital cities and predicted the seizures would put a "significant dent" in drug supply "for some time".

The arrests were part of Strike Force Baranbali - an ongoing investigation into Italian organised crime sydnicates.

Griffith Police crime manager Paul Smith said tip-offs from the public were critical in the success of the operation.

"I want to personally thank the public for their assistance and assure them that their information will be investigated and acted upon by police," Det Insp Smith said.

"This result would not have been possible without public information."

Anyone with information relating to the illegal drug trade should call Griffith Police on 6969 4299 or Crime Stoppers on 1800 333 000.