BEIJING - China's food safety authorities are carrying out studies in the hope of finding ways to detect "gutter oil," Vice Health Minister Chen Xiaohong said Friday at the national food safety and health inspection meeting.

Chen didn't give details on the latest development of the studies.

Several food safety scandals surfaced in 2011, including gutter oil, or oil illegally made by reprocessing waste oil from restaurants, and then marketed and re-used as cooking oil by profiteers.

Though a nationwide campaign has been launched to stamp out gutter oil,some scholars have warned that it is difficult to test for, because profiteers are already sophisticated enough to fool inspection devices with their illegal wares.

Chen added that China set up a national food safety risk assessment center in 2011, acquiring some 800,000 sets of statistics throughout the year.

To date, six "blacklists" have been released, including 64 illegal food additives and 22 abuse-prone food additives, following food safety risk assessments, Chen said.

The food safety risk monitoring network has covered 244 municipal and 716 county level areas, targeting food contaminants and food-related diseases.

Chen also said at the meeting that China has instituted nearly 20,000 drinking water-monitoring sites across the country.