JINAN -?A total of 134 people in East China's Shandong province were arrested last year for producing and selling "gutter oil," a local court official said Tuesday.

Nineteen people have been prosecuted thus far, with 12 government officials losing their positions for their dereliction of duty, said Zhou Yuhua, head of the Shandong provincial higher people's court.

In one case, two people were both sentenced to 10 years in prison for producing and selling more than 110 tonnes of gutter oil, an illegal food additive that is made by processing used vegetable oil, Zhou said.

China launched a nationwide food safety campaign in August 2011 to clamp down on the illegal practice of making and selling gutter oil.

China's food safety authorities are carrying out research to discover new methods of detecting the oil, Vice Health Minister Chen Xiaohong said at a national food safety meeting held in mid-January.

Scientists have warned that it is difficult to test for the substance, as profiteers have already become sophisticated enough to fool inspectors.