NINGBO - Chinese customs officials have intercepted 1,127 tonnes of imported waste metals from Japan with excessive gamma rays in the coastal city of Ningbo in east China, local authorities said Tuesday.

The radiation levels of the waste metals, imported by a recycled metal company in Ningbo, was twice the national standard and hazardous to the human body and the environment, according to Ningbo customs.

The metals contained caesium-137, a radioactive isotope of caesium. Small amounts of caesium-137 were released into the environment during nuclear weapon tests and nuclear accidents, most notably the Chernobyl disaster.

Ningbo customs has ordered the cargo to be returned and has handed the case over to the anti-smuggling department for further investigations.

Ningbo customs has intercepted a total of 8,544 tonnes of waste imported metals with excessive radiation from Japan since the Japanese nuclear disaster of March 2011, said Wang Lingbao, a logistics control department official with the customs.