Eleven coaches have been seized from a Co Tyrone hiring company as part of a crackdown on fuel fraud.
HM Revenue & Customs officers took the vehicles from Kelly Coaches in Sixmilecross near Omagh on Thursday after discovering kerosene - a fuel normally used for home heating - in the running tanks.
Business records were also removed from the premises.
Mike Connolly, assistant director of specialist investigations at HMRC, said:
"Legitimate businesses are already facing difficult times and it is wrong that they should be undercut by those involved in this type of fraud."
Kerosene costs around a third of the price of fully-taxed diesel. Mr Connelly said that use of the illegal fuel was giving rise to "unfair competition".
"It isn't about cheating the Government out of a few pounds, it's about depriving our public services of vital funding," he said.
"We want businesses to be able to operate without the threat of unfair competition."
HMRC has encouraged anyone with information on fuel fraud to make contact.
© UTV News