Radiation levels found in 1,127 tons of scrap metals imported from Japan exceeded China's regulated safe levels three times over, authorities with Zhejiang Ningbo's customs said on Wednesday.

The metals came from Japan's Chiba Port , a port near a nuclear plant that was crippled after Japan's earthquake. The radiation level was Cesium -137, and local customs officials said the cargo was prohibited to enter China, according to the country's law.

Dai Weigu, deputy chief of Ningbo Zhenhai Customs' department of logistics monitoring, said the cargo was added to their "list of special attention" when they received its entry declaration. "We figured it came from Chiba Port, the area with high radiation risk," said Dai.

He said the radiation detector's alarm went off during the discharging process at Zhenhai's port on June 4.

This is the second time Zhejiang Ningbo's customs has tracked high radiation levels this year.