The largest NSW marijuana bust in a decade has resulted in almost $22 million worth of crops seized and four men charged following a police raid on a northern NSW rural property.

Detectives on Wednesday uncovered a 49-hectare property at Gibberagee, about 52km southeast of Lismore, and allegedly seized 7200 cannabis plants and about 50kg of cannabis head with a potential street value of $21.6 million.

The property, allegedly used solely for the purpose of marijuana cultivation, contained 20 industrial grow houses, each equivalent to the size of an Olympic swimming pool.

Four men aged 20, 34, 35 and 37 were arrested at the property and charged with cultivating large commercial quantities of a prohibited plant and participating in a criminal activity.

NSW Police Assistant Commissioner Stuart Smith said in a statement on Thursday the investigation had dismantled an organised criminal syndicate operating across the state.

He said a total of 12 people had been charged as part of investigations into the syndicate and $41 million worth of cannabis had been seized.

“Criminals who profit from cultivating these drugs are often known to reinvest funds into other criminal enterprises that directly impact the communities of NSW,” Mr Smith said.

The four men were all refused bail to appear at Lismore Local Court on Thursday.