Shanghai will carry out full-scale checks on feed used in the fisheries industry due to fears that the widening melamine-tainted food scandal may spread to seafood.

Dangerous levels of the chemical have already been found in eggs and milk powder.

Shanghai's Livestock Office said yesterday that the checks would cover more than 100 feed producers in the city. Further inspections on seafood would start if any food given to fish was found to be contaminated with melamine.

Four brands of melamine-tainted eggs have been discovered so far this week in Hong Kong and Hangzhou, capital city of Zhejiang Province.

It is believed the melamine was added to feed given to chickens that laid the contaminated eggs.

The level of protein is a key element in determining food standards in China. Melamine raises protein readings but not the protein content.

The chemical is a banned animal-feed additive, according to a notice issued by the Ministry of Agriculture in July 2007.

Shanghai Evening Post yesterday cited an industry insider as saying that adding melamine in feed is a common practice as producers seek to raise protein readings at less expense.

The chemical, used to make plastics, paint and adhesives, has been used in the feed industry for at least five years, the insider told the evening newspaper.

The source added that cows, sheep, poultry, pigs and fish had been given food containing melamine.

Soft-shelled turtles and eels were also on the melamine list, especially in southern China, the paper said.

Melamine waste residue is sold by its producers for between 600 yuan (US$87) and 800 yuan a ton to animal feed firms. Those companies then add the melamine residue to feed and sell that feed for up to 4,000 yuan a ton on the market, according to the newspaper.

The chemical, which can lead to kidney stones and life-threatening renal failure, was at the heart of last month's dairy scandal that swept China.

The newspaper also said that a professor at one of China's top academic institutions has denied that his invention of an animal-feed addictive was the origin of the melamine-egg outbreak.

Gao Yinxiang, a professor at the Graduate School of the Chinese Academy of Sciences, said his invention "DH Protein Feed Additive Technology" patented in 1999 would not produce melamine.

Gao said his technology was meant to produce food for ruminants as they had the stomachs that can break down non-protein nitrogen.

Meanwhile, the legal representative of a feed factory had been arrested after melamine was discovered in its products, according to the Dalian Hanwei Enterprise Group, whose eggs were first found to contain the chemical.

Beijing News yesterday quoted Han Wei, president of Dalian Hanwei, as saying that the unidentified legal representative of Shenyang City-based Xinmin Mingxing Feed Factory was in police custody.

The government in the northeastern city of Dalian in Liaoning Province has said it was first alerted to the problem of melamine-tainted eggs on September 27.

City authorities recalled tainted eggs, suspended exports and sent inspectors to the company, according to a notice on the Liaoning Province Animal Health Bureau Website.

It remained unclear why the bureau did not publicize the discovery of the melamine-contaminated eggs when they were first found.

(Shanghai Daily October 31, 2008)