Police in northern China have arrested 27 people in their probe into tainted milk that has sickened 53,000 children and embarrassed China's reputation abroad, state media reported Tuesday.
The 27 are among 36 detained since law enforcers in Hebei province started investigating Sanlu Group, the company at the centre of the scandal, earlier this month.
It followed the discovery that the industrial chemical melamine, which is normally used to make plastics, had been added to Sanlu powdered milk.
The Xinhua news agency had reported 22 detentions by Monday, and said they were involved in a network that made and sold melamine and added it to milk.
Four children so far have died after drinking milk tainted with melamine, which can make watered-down milk appear richer in protein.
According to police investigations in Hebei, where Sanlu is headquartered, the melamine was produced at underground plants and sold to breeding farms and purchasing stations, the China Daily reported Tuesday.
It said Chinese officials, learning that the purchasing stations were among the key links in how the contaminated milk spread, have kicked off a national campaign to overhaul the system.
Althogether, 31 provinces have set up special task forces to supervise the purchasing centres and implement more standardised practices, the paper said.
As the tainted milk scandal has multiplied, a growing range of China-made products abroad have been pulled off shelves.
British sweetmaker Cadbury said Monday it found had traces of melamine in products made at its Beijing factory, and recalled products made there and on sale in Hong Kong, Taiwan and Australia.
Indonesia's food supervisory agency said at the weekend that it discovered some 16 Chinese-made diary products contained melamine, adding that all those products -- including well-known brands such as Snickers and M&M's chocolates -- would be immediately destroyed.
Mars said it was "extremely surprised" by that decision, insisting other tests had cleared its products of contamination.
More than a dozen Asian and African countries, plus the 27-member European Union, have taken steps to ban or limit consumption of Chinese dairy product imports.