GARDAI today resumed their search of a Co Wicklow cannabis farm capable of producing €1m of the drug a year.
Yesterday, gardai found a sophisticated cannabis growing facility at the farm at Donard in west Co Wicklow and 400 cannabis plants worth an estimated €250,000.
They also found a heating and irrigation system being used to "hothouse" the crop in the industrial sized growing operation.
It was capable of producing cannabis with a street value of €250,000 every two months.
While gardai estimated that 400 plants were found, sources said that such was the size of the facility that further searching was required today before a final total could be reached.
A 36-year-old lrish man was arrested at the scene and was taken to Naas Garda Station for questioning where he is being held under Section 2 of the Drug Trafficking Act. He can be held for up to seven days.
Gardai suspect that the factory was being run by an organised crime gang and further inquiries into the seizure are underway.
The find was uncovered when Customs officials stumbled across the cannabis as officers carried out routine sampling of fuel in nearby vehicles.
Local gardai from Baltinglass and the National Drugs Unit were called in to examine the find and seized more than 400 cannabis plants and hi-tech cultivation equipment.
Revenue and Customs confirmed its officers from Dublin Port were in the area at around 8am for a routine oil sampling investigation when they discovered the cultivation factory.
Forensic officers remained at the scene throughout the day examining the seizure.
Gardai have also been tackling the problem under Operation Nitrogen, set up to detect cannabis growing houses.
Drug officers have located three other cannabis factories in recent weeks in Meath, Galway and Donegal and seized almost 1,500 plants with an estimated street value of €760,000.
In the last three years several cannabis factories have been detected in houses, many along the border, where Asian gangs moved in to cultivate the plants.
The recession has forced the big crime gangs into cannabis cultivation because of their need to "diversify" and raise sufficient cash to fund the purchase of major drug shipments.
One senior garda said: "This is just another arm of the organised crime racket. The gangsters are like businessmen. They spot a new growth area and move in quickly to grab a profit."
The Co Wicklow find produced further evidence that Irish organised crime gangs have spotted the financial potential in the cannabis cultivation racket.
They have replaced Chinese criminals who have been almost forced out of business by successive garda operations.
The senior garda added: "The Chinese sold off their equipment to the Irish criminals and possibly passed on some of their expertise although information has always been available on the internet."
Fine Gael justice spokesman Charlie Flanagan said the discovery of the cannabis operation in Wicklow reveals the country is faced with a new and significant problem of home-grown drug production.
"While there have been other similar discoveries made by gardai, the scale of this illegal operation is a seriously worrying development," said Mr Flanagan.