A probe into fuel laundering and smuggling in Northern Ireland has been launched by a committee of MPs.
The Northern Ireland Affairs Committee wants to determine the amount and extent of the problem.
The impact of the border with the Irish Republic on the illicit trade, the role and effectiveness of the Organised Crime Taskforce and the extent to which organised criminal gangs are profiting will be examined.
Fuel is smuggled across the border to exploit the difference in duty rates. It is also laundered so that low-tax red diesel can be passed off as a higher duty type.
In March the UK's largest ever fuel laundering plant was dismantled by HM Revenue & Customs (HMRC) in Northern Ireland.
A customs spokesman said the "industrial scale plant" was capable of producing more than 30 million litres of illicit fuel a year, the equivalent of £20 million in lost revenue.
The plant was discovered in a raid in Crossmaglen, County Armagh.