Four charged in $10m Sydney cannabis bust

Four men have been charged following the dismantling of a major cannabis syndicate in which 2242 plants with an estimated street value of $10 million were seized in Sydney's southwest.

Elaborate hydroponic set-ups were found in six homes raided at Narellan, Spring Farm, Elderslie, Mt Annan, Gregory Hills and Oran Park on Thursday.

"In my 27 years in the police, these are amongst the most sophisticated hydroponic set-ups I've ever seen," Detective Acting Superintendent Jason Smith told reporters on Thursday.

Two men, aged 25 and 31, were arrested at the Oran Park home and a 39-year-old man was arrested at the Mt Annan Property while a fourth man, 33, was arrested at Cabramatta.

The men were allegedly part of a single syndicate which police estimate would have been producing millions of dollars worth of cannabis per year.

All four were charged with various drug offences of a commercial quantity.

Acting Supt Smith said the houses were located in densely populated residential areas.

"There would have been families with children living within metres of dangerous chemicals and hazardous wiring that could potentially catch fire or electrocute someone."

Thursday's raids followed a lengthy investigation, and police believe they have made a sizeable dent in Sydney's drug market.

A separate operation on a home in the nearby suburb of Green Valley on Wednesday uncovered more than 175 cannabis plants estimated to be worth more than $500,000.