Three men linked to a "sophisticated" Co Armagh diesel laundering plant capable of producing 22 million litres of illicit fuel a year have been sentenced.
The sheer scale of the set-up would have meant £19.6m in lost duty and taxes annually.
Newry Crown Court had been told the tax evasion ran into "millions of pounds" and involved "a criminal operation with undisclosed figures in the background".
HM Revenue and Customs (HMRC) officers began investigating Padraigh Doran (33), Martin Fitzpatrick (35), and Micheail Kennon (25), after a large laundering plant was discovered at Kilnasaggart Road in the Jonesborough area in January 2013.
HMRC officers seized 39,000 litres of laundered fuel, two fuel tankers, 62 bags of bleaching earth - used to launder the diesel - and 18,000 litres of toxic waste from the site.
The operation included a purpose-built underground storage facility to hide illegal fuel, which was capable of storing over 100,000 litres. An agricultural shed had been built over the top of the storage facility in an attempt to disguise the activity.
At a previous hearing in January 2017, the three men had pleaded guilty to fraudulent evasion of Excise Duty contrary to Section 170 of the Customs and Excise Management Act 1979.
All three men were sentenced when they appeared at Newry Crown Court on Tuesday.
Doran (33), a mechanic from Macullagh Road in Newtownhamilton, was also sentenced for a separate fuel fraud offence after he was caught driving a van carrying 2,400 litres of laundered fuel in November 2014.
He was handed two concurrent 18-month prison sentences, suspended for three years.
Self-employed lorry driver Fitzpatrick, from Main Street in Newry, was sentenced to 18 months imprisonment suspended for three years.
He had admitted allowing his vehicle to be used to carry the illegal fuel.
He served a two-year prison sentence in England in connection with a £80,000 alcohol tax evasion scam.
Unemployed farmer Micheail Kennon (26) from Newtown Road in Belleeks, was also sentenced to 18 months imprisonment suspended for three years.
Each of the men's DNA was discovered on gloves, face-masks and respirators.