Customs in northeast China's port city of Dalian ordered the return of over 688 tonnes of solid waste back on Wednesday. The aluminum waste was accompanied by fake documents, and was believed to have been smuggled into the country in 2018 from Australia via Hong Kong, according to customs officials. Suspects have been detained and a further investigation is underway.

Aluminum slag, mainly composed of gray particles, is a kind of industrial waste residue that would cause serious pollution to environment if deposited at the port for a long time.

It was the second batch of illegally imported foreign garbage that Dalian customs has ordered out of the country this year. It comes after the Chinese government banned waste imports last year. The country began to import solid waste as a source of raw materials since the 1980s and was the world's largest importer for years. However, its weak capacity in garbage disposal as well as smuggling foreign waste into the country for profit have posed a threat to both the environment and public health. 

Chinese customs reported that they had dealt with more than 400 smuggling cases of 1.55 million tons of wastes in 2018. Dalian customs officials said they will continue to take effective measures in risk assessment, sampling inspection, and tracking disposal, to ensure "foreign garbage" goes back to where they originated.