A court in Ningbo, Zhejiang province, has upheld an original criminal sentence on seven suspects involved in manufacturing huge amounts of gutter oil.

Liu Liguo, the head of a gang that had refined and sold gutter oil since 2007, and six people working for him, were convicted of producing and selling hazardous and substandard food, according to a final verdict issued on Friday by the Higher People's Court of Zhejiang province.

Gutter oil refers to recycled oil made from kitchen waste dredged from gutters behind restaurants as well as inedible animal oil. The oil, which contains carcinogenic substances, is dangerous if consumed.