Manufacturers of animal feed will be more closely monitored following the latest food safety scare involving eggs contaminated with melamine, th-e Ministry of Agriculture said on Friday.

A worker grades eggs after they have passed through an ultraviolet disinfection scanner at a factory in Beijing on Friday. [Agencies]

This week, four brands of eggs were found to contain the chemical, and several experts have pointed the finger at chicken feed as the likely source.

A ministry rule forbids firms from adding melamine to food intended for animals, Wang Zhicai, director of the ministry's husbandry and livestock division, said in a statement posted on the ministry's website (agri.gov.cn).

However, initial investigations have shown that some producers deliberately added the chemical to their feed products.

"The ministry will tighten its supervision of the feed industry and crack down on producers who add melamine to their products," Wang said.

Despite the recent allegations and controversy, Wang said that in June of last year, a "rigid" standard was introduced for testing the level of melamine in feed, following a scandal over contaminated feed exported to the United States that killed hundreds of pets there.

The limit was set at 2 mg/kg, and any products that recorded a level above that should be sealed and destroyed, he said.

"Producers violating the rule will face severe punishment: They could have their business license stripped or face criminal charges," he said.

Despite Wang's claims, food contaminated with melamine continues to find its way on to the market.

In September, dairy products tainted with melamine claimed the lives of four babies and made thousands of others sick.

Wang said that since then, the agriculture ministry has sent more than 369,000 inspectors to some 250,000 feed producers, whose work led to the closure of 238 firms that were operating illegally.

Some 3,682 tons of feed were also confiscated and destroyed, he said.

Although it is against the law to add melamine to food, industry sources have said it is not compulsory for feed producers to test for the chemical, although some leading firms do so voluntarily.

The practice of mixing melamine into animal feed is an "open secret" in the livestock and fish food industry, the Nanfang Daily reported on Thursday, describing a process of repackaging melamine scrap into an inexpensive product called "protein powder", which is then sold to feed suppliers.

Health experts have said that while a small amount of melamine poses little danger to people's health, larger doses can cause kidney stones and lead to kidney failure.

Agriculture officials said at a press conference in Guangdong on Friday that following inspections of 581 samples of animal feed conducted since last Saturday, eight were found to be contaminated.

Provincial authorities claim to have destroyed 6.48 tons of substandard products.

Premier Wen Jiabao, who was on a visit to Kazakhstan, told reporters in Astana on Friday that it would take the government up to two years to regulate the problematic food industry.

(China Daily November 1, 2008)