To fight this major crime, European inspectors have had to turn to forensic data analysis, mobile X-ray machines, DNA labs and a whistleblowing website.
The object of their attention? Contraband garlic.
Evading customs duties on Chinese garlic is a big problem in the European Union, with authorities saying they have been deprived of tens of millions of euros in lost taxes.
In the latest development, prosecutors suspect two British men are involved a massive smuggling scheme that brought nearly 1,000 tonnes of illicit garlic into Sweden.
"I don't know of other cases this large of smuggling of ordinary goods," Thomas Ahlstrand, deputy chief prosecutor of the International Public Prosecution Office in Gothenburg, said in a telephone interview.
He said the smuggling ring, which is might have included Britons, Dutch and Belgians, unloaded several shiploads of contraband in Norway and transported the garlic by truck through the open border with Sweden.
In an unrelated case, a British court last month imposed a six-year sentence on Murugasan Natarajan, the owner of a London import-export firm. He was found guilty of evading $3.2-million in customs duty after investigators intercepted seven tonnes of smuggled garlic.
Investigators got suspicious when they inspected containers that were supposed to contain ginger, which is free of duty. The temperature in the containers was too cold for ginger but perfect for garlic.
Mr. Natarajan was tried in absentia after he skipped bail and is now a fugitive. The judge who sentenced him said the fraud was "sophisticated, persistent and prolonged."
"We're talking big money," British customs spokesman Andrew Bennett said in an interview.
An Irish food importer got an equally stiff sentence this spring. A Dublin court handed Paul Begley a six-year sentence for failing to pay duty on 1,000 tonnes of Chinese garlic, which was mislabeled as apples.
Another recent case involved 144 tonnes intercepted in Poland.
China produced 18,560,000 tonnes of garlic in 2010, 82 per cent of the world's output, according to the United Nations' Food and Agriculture Organization. Growers from other countries complain that they cannot compete against the cheap, abundant Chinese crop.
To protect its garlic producers, most of them Spanish farmers, the EU first imposed in 1993 an import quota on Chinese garlic. This was replaced in 2001 by a 9.6 per cent customs duty on Chinese garlic, with an additional duty of €1,200 per tonne.
Since then, garlic smuggling cases are, after meat and sugar, the third most common type of agricultural investigations probed by OLAF, the anti-fraud office of the European Commission.
"Fraud and irregularities with Chinese fresh garlic have occurred since the nineties, but these facts have only had real financial implications for the EU budget since 2001," OLAF spokesman Pavel Borkovec said in an e-mail to the Globe and Mail.
"A container-load of say 25 T of frozen garlic has a potential risk of €30,000 in terms of evaded customs duties."
Smugglers typically forge documents such as bills of lading and shipping manifests, claiming that their containers hold other farm products. Others use bogus certificates of origin to obscure the garlic's origin.
When quotas were introduced in 1993, OLAF investigators noticed that there was a sudden increase in garlic imports from countries that previously were not a source of the bulb. Those countries, such as Iran or Malaysia, were however along shipping routes for goods from China.
In another case, a shipment intercepted by Austrian customs was labelled as single-bulb wild leek, which is duty-free. DNA tests showed however that the merchandise had been mislabeled to evade duty.
Mr. Borkovec said organized crime might be involved in some of the fraudulent importations.
"Sometimes these organizations do not limit themselves to garlic smuggling, but illegally import other commodities as well (textiles, footwear, etc)," he said in his e-mail. "In addition, evidence shows that illegally generated revenues from smuggling are used to finance other types of criminal activities."
Editor's Note: An earlier version of this story incorrectly reported that arrest warrants had been issued for two British men suspected of being involved in a smuggling scheme in Sweden.