SHANGHAI--Criminal networks are smuggling plastic trash from the West to illegal recycling plants in Asia, profiting from a 2018 ban on waste imports in China where the bulk of used plastic was previously processed, Interpol said on Friday.

The decline in the number of legal export channels for millions of tons of waste has “opened the door to illegal business opportunities,” the police organization said in a report, resulting in a surge in illegal trade and waste treatment.

China started importing waste in the 1980s, when ships delivering goods to Europe or the United States returned laden with potentially profitable recyclable materials.

But Beijing put an end to the business in 2018 to upgrade its economy and force recyclers to tackle the surging volume of domestic waste lying untreated in huge landfill belts surrounding all of its major cities.

Interpol’s global pollution enforcement team said criminal gangs have since taken advantage of the disruption to global supply chains that previously saw more than 7 million tons of scrap plastic arrive at China’s ports every year.

It said “there has been a considerable increase over the past two years in illegal waste shipments, primarily rerouted to Southeast Asia via multiple transit countries to camouflage the origins of the waste shipment.”

There has also been an increase in illegal waste incineration and landfills in both Europe and Asia, with gangs using fraudulent documentation to evade regulations, it said.

Environmental group World Wide Fund for Nature (WWF) said the removal of China as an “easy solution” for the world’s plastic waste problems had allowed criminal gangs to flourish, and called on governments to establish a global framework to tackle the issue.

“Waste crime is a rising threat with roots in a more fundamental problem: the inability to manage our plastic use and production,” said Eirik Lindebjerg, WWF’s Global Plastics Policy Manager.