A DIAC spokesman said the raids, which took place overnight on Monday, netted eight Malaysian nationals, including seven males and one female, who have been working on farms in the Sale area.

The spokesman said eight Malaysian nationals were detained at Marybrynong Detention Centre for being unlawfully in Australia or for being in breach of their visa work conditions.

He said 10 others who were issued notices of intention to cancel visas included two Malaysians, four Indonesians and four Nepalese.

A female Indonesian national's visa was also cancelled and she was placed on a bridging visa while outstanding immigration matters were resolved.

While the spokesman said all illegal workers were found living in the Sale area, he would not say how many or which farms were raided.

The raid comes after a similar operation in Sale on August 11 which netted 23 illegal workers, with 22 being transferred to the Maribyrnong Immigration Detention Centre.

Those detained in that raid included 13 Malaysian nationals, seven people from Vietnam and two from China.

The spokesman said the latest raid was made possible by information received from members of the community and other services.

He said illegal worker warning notices were issued to employers of the people found during the raid.

"The Department of Immigration and Citizenship reminds employers they are required by law to check if employees are legally entitled to work in Australia,'' he said.

The spokesman also said while it was the labour hire organisations that were in the spotlight, there was also an onus on the farm owners to have asked the "relevant questions'' to ensure the employees were allowed to work in Australia.

"Employers convicted under Commonwealth legislation can face fines of up to $13,200 and two years' imprisonment,'' he said.

"And companies face fines of up to $66,000 per illegal worker.''

The spokesman urged employers to access the Visa Entitlement Verification Online service to confirm workers were eligible to work in Australia.

Anyone with information about illegal workers or visa overstayers should phone the Immigration Dob-In Line on 1800 009 623.