The compliance operation by DIAC officers will result in 22 foreign workers being sent home after they were detained, suspected of working illegally on local farms.

The operation took place overnight on Tuesday, with 22 of the 23 workers being transferred to the Maribyrnong Immigration Detention Centre.

While a DIAC spokesman said all illegal workers were found living near Sale, he would not say how many or which farms were raided.

He said those detained included 13 Malaysian nationals, seven from Vietnam and two from China.

He said the remaining person was granted a bridging visa so she could be reunited with her child and organise her own departure from Australia.

One additional person was counselled regarding working conditions on his student visa.

All 23 people were working either while unlawfully in Australia or in contravention of no work conditions on their visas.

The spokesman said the department had visited a number of farms in the Sale area to interview employees.

He said from there, each workers' details were taken and DIAC conducted checks before deciding to detain them.

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

He said many employers wrongly assumed because a person had a Victorian driver's licence or a current visa or passport, that they were allowed to work in the country.

He said the immigration compliance operation served as a warning that ''breaches of immigration law will not be tolerated''.

''This operation demonstrates that if people work illegally or if people employ illegal workers, they will be caught.

''Employers can face severe penalties for hiring people who do not have work rights in Australia and the department will be seeking information on any involvement of organisers behind this illegal employment.''

Employers convicted under Commonwealth legislation can face fines of up to $13,200 and two years' imprisonment, while 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 call the Immigration Dob-In Line on 1800 009 623.