Customs in the east China city of Xiamen recently intercepted an illegal import of over 1,400 tonnes of solid waste.

It was the largest single case by volume after customs, environmental protection, public security and quality control authorities jointly launched a crackdown on solid waste imports in March.

In August, a Xiamen-based trade company applied for the clearance of 51 containers of imported "zinc ore," weighing 1,415 tonnes.

However, customs officers discovered apparent differences in the substance's appearance with normal zinc ore and sent samples for examination.

It was later identified as zinc residue left after smelting, which is subject to an import ban in China. Recycling of zinc residue generates pollutants that can contaminate water and soil.

Since late February, Xiamen customs have discovered 19 instances of illegal solid waste imports and seized nearly 40 suspects.