Beijing banned the sale of turbot on Monday after detecting excessive amounts of carcinogens in the fish.

A 12315 hotline has been set up so that citizens can report sales of the contaminated fish, according to the municipal food security office.

Several other cities and provinces -- including Tianjin, Xi'an and Liaoning -- have also started quality inspections of turbot after Shanghai announced Friday it had detected excessive residue including nitrofuran and chloromycetin in 30 samples of turbot. The chemicals are known cancer causing agents.

The finger has been pointed at fish farmers who knowingly feed banned chemicals to the fish.

Fish markets, shopping malls, and hotels in Shanghai have stopped selling turbot following government warnings.

The eastern province of Shandong, a major turbot producing area, has taken measures to monitor turbot farms.

It has also called on local authorities to trace contaminated fish and crank up inspection efforts in the cultivation, transportation, storage and sales of turbot and other fish.

Due to their low resistance to disease, the fish, introduced from Europe in the 1990s, are sometimes fed large quantities of medicinal supplements, which leave harmful, cancer causing residue in their flesh.

The State Food and Drug Administration has ordered local offices and authorities in coastal areas including Shandong, Jiangsu, Hebei, Zhejiang, Fujian, Guangdong, Liaoning, and Tianjin to closely monitor the case.

China is currently assailed by severe food security problems as suspect food products continue to come to light. Recent cases include parasite-infested snails, steroid-tainted pork and ducks and hens that were fed cancer-causing Sudan dye to make their yolks red.

(Xinhua News Agency November 21, 2006)