Traces of melamine were found in nearly 12 percent of milk powder products that were tested in the country, Chinese authorities confirmed. This is one of the biggest food contamination scandals that has so far sickened 53,000 children and killed four.
As China marked its national day, President Hu Jintao said lessons must be learned from the scandal over tainted milk that has soiled China's reputation and led to a series of bans or curbs on its dairy exports worldwide.
The Anglo-Dutch company Unilever became the latest big-name brand to recall some Chinese products, taking Lipton milk tea powder off shelves in Hong Kong and Macau after tests showed them contaminated with melamine .
The chemical is normally used in making plastic, but can make watered-down milk look richer in protein than is actually the case.
"Food safety is directly linked to the well-being of the broad masses and the competence of a company," Hu said during a tour Tuesday of dairy companies in eastern China's Anhui province, the Xiinhua news agency reported.
"Chinese companies should learn from the lessons of the Sanlu tainted milk powder incident," he said, referring to Sanlu Group whose toxic baby formula was at the origin of the crisis.
Hu urged companies to strengthen management and food safety checks and make sure their products were safe for consumers, according to Xinhua.
Since the scandal first erupted last month, an increasing number of dairy products have been found to contain the industrial chemical melamine.
A sweeping nationwide check has found melamine in 31 milk powder products, representing 11.7 percent of a total of 265 products put to the test, said the General Administration of Quality Supervision, Inspection and Quarantine, the nation's top product safety watchdog.
All had been produced before September 14, it said in a statement on its website, insisting products made after that date were safe.
They came from 20 different companies, including Sanlu Group and several of its partner enterprises.
The agency said it had checked 154 companies altogether, representing more than 70 percent of the entire market for milk powder.
A series of countries, mainly in Asia but also in Europe and Africa, have slapped bans or restrictions on imports of some Chinese milk products, while many companies have simply pulled items off the shelves.
British sweet maker Cadbury recalled 11 China-made chocolates from shops in Australia, Hong Kong and Taiwan, although Hong Kong's food safety agency said Wednesday their melamine level was below the legal limit.
As public anger grows over the scale of the crisis, the local government at the epicentre apologised for covering up the scandal for weeks.
In northern China's Shijiazhuang, where Sanlu is headquartered, authorities issued an unusual apology for having responded in a belated manner, the China Daily reported.
Wang Jianguo, a spokesman for the Shijiazhuang leadership, said the local government felt "a deep sense of guilt and regret" over the babies poisoned by melamine.
He said the government received reports from Sanlu Group on August 2 that some milk powder caused kidney stones, but waited until September 9 to pass on the report to the next level in the system, the Hebei provincial government.
Instead of alerting their superiors, Shijiazhuang officials offered medical treatment to patients, urged Sanlu to import inspection machines and recalled the company's milk powder, the paper said.
Sanlu also asked for government help in keeping a lid on the scandal, the People's Daily reported, citing Wang.
He said Sanlu wrote to the government in Shijiazhuang asking it to monitor milk quality and take legal action against people adding melamine.
It also asked officials "to strengthen management, control and coordination of the media, in order to create a favourable environment for the company's recall of problem products and prevent a negative impact on society by stirring up the issue," the People's Daily wrote.