It was in the local news a year or so back. If they go to any construction site, they will find so many cases that they won't have resources to do any other work related investigations for the rest of the year. As such they decided to stop doing it for the unforeseen future. From the politicians, they mostly want the companies to self regulate. Human trafficking for labor is costly to enforce and is not something which wins votes, and the shortage in low wage workforce has trickle down effects on political goals that they do care about.
The situation is very similar in areas of farming (as the article describes), fishing, foresting, and cleaning.
Are you using "human trafficking" when you mean "hiring workers who lack documentation"? These are not the same thing, and I don't believe anyone who knows enough English to have encountered that term would make that mistake.
70% of all human trafficking is for forced and exploitative labor.
Lets take an example. 30 workers get transported over the border as seasonal workers to work at a farm. They live in small building without heating or running water, and barely have enough food. 3 months goes by and they have still not get paid, and when food stop arriving they decide to go to the police.
The owner of the farm claim innocence, as they simply hired contractors. There is even a ongoing legal case between the farm owner and this contractor because the work has been less than what was agreed and paid. The farm owner has been living in a different country for this whole period and never seen the workers, and the pickup for the produce was handled by a different contractor.
The police now have 30 unknown persons from multiple countries and without passports. The workers want to get their pay, and also food and shelter. They are do not want to get sent back home with nothing. The police will now have to do a lot of hard work, social service will have to address the humanitarian situation, and the criminals are very unlikely to be caught, fined and sentenced. It will cost a lot of money and resources for the government, with nothing that they can use political to show for it.
Under the laws I live on, this is human trafficking. There are an unlimited amount of variation this, but the key aspects are exploration under coercion, abduction, fraud, and deception. There are those that like to think the problem is just a few missing documents, but in practice there are victims being coerced and forced into doing dangerous work with little or no pay, and then treated with disinterest by the rest of society.
The situation is very similar in areas of farming (as the article describes), fishing, foresting, and cleaning.