BEIJING, CHINA - Police in China have detained the sacked chairwoman of Sanlu Group, the company at the centre of a mounting national scandal over deadly baby formula, state media reported on Wednesday.

A top local official in the northern city of Shijiazhuang, where Sanlu is based, has also been sacked over the food safety crisis, according to Hebei.com, an official news website in Hebei province.

Tian Wenhua, who was fired by Sanlu on Tuesday, was detained under laws governing the production and sale of harmful food products, said the site.

The sacked official was Shijiazhuang's Communist Party vice secretary Ji Chuntang.

China said Wednesday more than 6,000 babies had fallen ill and three died after drinking milk powder laced with a toxic chemical, as it vowed massive efforts to contain a widening food scandal.

The controversy, which first came to light last week, had originally centered on Hebei-based Sanlu, whose affected products have all been recalled.

However, authorities say a total of 22 companies have been found to have melamine in their milk powder, and their products would also be recalled.

Melamine, a chemical normally used to make plastics and glues, appeared to have been added to make the products seem richer in protein.

State media reports previously said that four people had been arrested for contaminating the milk. Three were reportedly milk dealers.

Four local officials, linked with agriculture and quality control, were also sacked on Tuesday, the official Xinhua news agency had reported earlier.

The scandal is the latest to rock China's food industry, already tarnished in recent years by a series of health scares over dangerous products, some of which have been exported.

Melamine was also found in Chinese pet food exported to the United States last year that killed dogs and cats.