Minister for Immigration, Chris Evans, said compliance officers executed search warrants simultaneously at two addresses in Hillston on Tuesday night and visited six premises in Griffith yesterday where around 50 people were interviewed.

Six unlawful non-citizens, three men and three women, were detained in Griffith. All were Indian nationals.

In Hillston, another four Indian nationals, three men and a woman, were detained for working in breach of their visa conditions while an Indian man and a Pakistani man were also located and found to be unlawful non-citizens.

All 12 have been transferred to Villawood Immigration Detention Centre in Sydney where arrangements will be made for their removal from Australia.

Senator Evans said the 12 people were believed to have been working in the horticultural industry on several farms in the region. All originally arrived in Australia legally with valid visas.

The operation was part of an ongoing investigation into illegal workers in the area and conducted with the assistance of NSW Police.

Senator Evans said the Riverina operation had yielded evidence of possible worker exploitation and migration agent fraud.

"The Rudd Government takes a zero-tolerance approach towards illegal workers and similarly, there are no excuses for employers who engage workers without valid visas.

"It is the responsibility of employers to ensure they only employ people with the right to work in Australia and severe penalties can apply to people who hire workers who do not have valid visas."

Senator Evans said employers convicted under this legislation face fines of up to $13,200 and two years imprisonment while companies face fines of up to $66,000 per illegal worker.