Hundreds of angry motorists attended a public meeting at the Gateway Hotel in Swinford tonight on the growing contaminated fuel issue.
Dozens of car owners described at the meeting how their vehicles' engines have been destroyed by the bad fuel.
A number of petrol forecourts are believed to have been effected.
A garda investigation is now underway.
Chairperson of the meeting, Paddy McNulty, said they believe as much as €500,000 in damage has been caused to cars in the region.
David Gilmore, the owner of Gulf Oil in Swinford said he alone has 22 official complaints and a further four pending.
He said the problem is not confined to his forecourt.
He said there are no contaminants showing up in his fuel in laboratory tests.
Gardaí told the assembled crowd that they are liaising with the National Bureau of Criminal Investigation in Dublin.
"We have never seen anything like this before," said the garda spokesperson.
He said the BMW region seems to be the area hit with the contaminated fuel, and the problem does not seem to have effected Dublin or the east coast.
He also said customs had confirmed that they had 'dipped' all of the petrol forecourts in Swinford one month ago and tested the fuel for three common components added illegally to boost fuel profits. The petrol had tested clear.
"We need now to find out what it is that is causing the problem in the petrol," he said. He added that the investigation could be protracted and slow because of its complexity.
Full story in this week's Mayo Advertiser.