At least 30 WA businesses including market gardeners and abattoir could be prosecuted after being caught up in the massive investigation into suspected illegal labour rackets linked to a multimillion-dollar alleged crime syndicate.

Authorities have been stunned by the scale of what they have uncovered and there is evidence the crackdown is already resulting in vegetable shortages and price rises as growers struggle to get their crops to market.

About 190 illegal foreign workers have been detained during raids, which have exposed shocking work practices, including claims labourers were forced to live in sub-standard accommodation and raw sewage from overcrowded dormitories had been found near crops.

The City of Wanneroo yesterday destroyed part of a crop at a Carabooda property where a contamination risk had been identified after it was alerted by The Weekend West that workers were continuing to pick tomatoes.

Chris Morrison, director of City businesses, said the contamination risk was low but the food was destroyed as a precaution while tests were done.

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An investigation by The Weekend West has revealed that two brothers - Michael and Canh Le - charged over allegations they headed the criminal enterprise, have helped build a more than $40 million family business empire that includes property, aquaculture, restaurant supply, construction, beauty therapy and shed and steel fabrication. Another 20 people have already been charged in the long-running probe involving WA Police, Federal police, the Australian Crime Commission and several other agencies.

Five other WA businesses, including in Geraldton and Carnarvon, allegedly run their own indentured workforces, according to migrant workers who have spoken to The Weekend West.

The Corruption and Crime Commission will investigate whether the alleged syndicate's criminal activities went undetected for so long because of potential misconduct by public officials.

CCC operations director Kim Papalia said much of the alleged syndicate's commercial activities had happened in a highly regulated environment.

"Therefore any illegal and improper activities are unlikely to have occurred without the knowledge of and, in some cases, the assistance and co-operation of public officers," he said.

Acting Det-Supt Chris Adams said the scale of the alleged syndicate's criminal activities was still emerging but appeared to be far- reaching with ties to other networks interstate and overseas.

Fears of substandard fabricated steel being imported from Asia prompted the State Government's building safety inspectors to yesterday join Federal and State authorities probing the Carabooda-based TLF group.

Building Commission inspectors yesterday pored over a medical centre under construction in Karrinyup and buildings in Carabooda headquarters of TLF, which were allegedly built using steel fabricated by a TLF offshoot in Asia, to check they complied with Australian standards.

TLF Constructions had claimed on its website to have worked on major State Government projects including the Butler train station and the Perth city link.

But government agencies said those claims were not true.

WA Building Commission compliance director Sandy Randall said there was an emerging problem in Australia with importing non- compliant building or construction materials.

The Immigration Department revealed it had started deporting the first of the illegal workers and visa overstayers, who are from Malaysia, Indonesia and Vietnam.