They also seized more than 200 items, including a significant quantity of chemicals, precursors and solvents, as well as equipment used to manufacture prohibited drugs.

NSW Police drug and firearms squad Commander Detective Acting Superintendent Jayne Doherty said given the size of the set-up, it will take police a number of days to dismantle it.

"Initial inquiries into the clandestine laboratory suggests the operations of these men were planned and well-established," she said. "The laboratory itself was sophisticated in its design and contained significant quantities of chemicals and solvents used to manufacture prohibited drugs – in particular MDA."

"The efforts of investigators have disrupted what could have led to the large-scale supply of prohibited drugs in the community and together with officers across the state we will continue to target drug supply on all levels."

During the search of the homes in Minto Heights and Lugarno, police seized a firearm, an electronic stun device and ammunition. They also seized electronic devices, documentation and an amount of methylamphetamine.

All items will undergo further examination.

Police also arrested a 42-year-old Lugarno man in Bankstown at 1pm on Wednesday.

Both men were taken to Liverpool police station where the 41-year-old man was charged with manufacturing a large commercial quantity of prohibited drugs.

The 42-year-old man was charged with taking part in manufacturing a prohibited drug.

Both men were refused bail to appear at Liverpool Local Court on Thursday.

Investigations are continuing.

More to come