Australian police have extended an investigation into dozens of Irish nationals who have breached their holiday visa conditions by taking part in a sales scam across three states.

Last month the Sunday Tribune revealed that 19 Irish nationals had their visas cancelled and three individuals were deported from Queensland following an extensive police probe.

The Australian Department of Immigration and Citizenship now estimates that up to 50 Irish people are involved in shady trading in Queensland, South Australia, and Western Australia.

The Irishmen are reported to have been selling electrical and mechanical equipment, including generators and pumps, at inflated prices in the back of white vans, prompting local residents to report them to the authorities.

The Irish group recently came to the attention of police in South Australia, who reported the men to the immigration authorities and the office of consumer and business affairs.

A South Australian police spokeswoman told the Sunday Tribune that while the men were not guilty of any criminal offences, the contravention of their visa conditions was being treated as a serious matter.

"The Irish nationals came to our attention when they crossed the border from Victoria and started to sell electrical equipment in the Mount Gambier area," she said.

"They are on holiday visas which prohibit any form of work and following complaints from members of the public we handed them over to the immigration authorities and reported them to the office of consumer and business affairs.

"There were reports that up to 200 Irish nationals were involved but we don't believe that to be the case.

"We have received quite a lot of complaints from members of the public informing us that the goods on sale were substandard and overpriced," added the spokesperson.

Australian Consumer Affairs Minister Gail Gago has warned the public not to purchase the Irish group's goods.

Under Australian law, traders who travel from place to place selling goods or services more than $AUD50 are required to comply with the door-to-door sales provisions of the Fair Trading Act 1987, which includes providing the consumer with a 10-day cooling off period.