Portland and Hamilton police detectives raided a south Portland property about 7.30pm on Saturday, allegedly uncovering a "very sophisticated" growing network and plants worth nearly half a million dollars.

Detective Senior Constable Jarrod Anderson, of the Portland police crime investigation unit, said a search of the property uncovered more than 250 cannabis plants.

The property was unfurnished, included an electrical bypass system and was used solely as a grow house, the detective said.

"This was a very sophisticated, commercial set up," he said.

A 37-year-old Vietnamese national was arrested at the property.

He has since been interviewed and charged with drug offences, including trafficking a commercial quantity of cannabis.

Detective Senior Constable Anderson said the accused man was residing in Australia illegally.

The man appeared in Warrnambool Magistrates Court on Monday for a brief filing hearing.

He did not apply for bail and was remanded in custody until August 21 for a committal mention hearing.

Lawyer Dean said the man spoke very little English and had previously spent time in immigration detention but did not say why.

Saturday's raid continued a busy few weeks for south-west detectives and divisional tasking units.

A 47-year-old Heywood man was last month remanded in custody after police uncovered six large cannabis plants, 24 cannabis seeds and dried plant weighting over two kilograms, as well as 30 high-powered lights believed to be used in a hydroponic grow-house.

A 56-year-old Dartmoor man was also arrested in an unrelated police raid that uncovered six mature cannabis plant and two illegal firearms.

Earlier in March, a Warrnambool woman was busted with 20 grams of cannabis, drug paraphernalia and evidence of significant drug trafficking.

And two Vietnamese nationals were charged in relation to $140,000 cannabis drying operation found in a central Hamilton home.

Evidence seized at the Hamilton property led to a search warrant at a Horsham property which uncovered 280 cannabis plants. The drugs had an estimated street value of half-a-million dollars.

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