Chinese police have detained six people suspected of producing and selling melamine, the chemical at the center of the country's scandal over tainted dairy products, the official Xinhua news agency said.
The arrests were made in Hohhot, capital of the northern region of Inner Mongolia, which is China's main dairy-producing area, Xinhua said in an overnight report, citing the municipal government.
The arrests were made during an investigation into melamine contamination at Yili and Mengniu, two major dairy companies based in Inner Mongolia, it said.
Inner Mongolia Yili Industrial Group, Mengniu Dairy and Bright Dairy group were found earlier to have produced milk contaminated with melamine.
Xinhua did not say whether the suspects were connected to either of the firms. It cited Tian Min, vice secretary general of the municipal government, as saying the results of the investigation would probably be released in four to five days.
Thousands of children in China have fallen ill with kidney problems and four have died after drinking milk formula laced with melamine, a cheap industrial chemical that can be used to cheat quality tests.
China's latest food safety scare has also prompted mounting recalls and warnings abroad, as traces of the chemical have been found in a wider range of dairy products.
The arrests follow the detention last week of 22 people in Hebei province suspected of being involved in a network there for producing melamine and selling it on to milk farms and purchasing stations.