China's quality watchdog has found that a dairy company in Zhejiang province has added protein powder extracted from dirty hydrolyzed leather waste to enrich the protein content in their products, CRI reported today.

According to the report, leather protein powder is believed to be harder to detect than the industrial chemical melamine which caused a food scare in China. Melamine-contaminated milk sickened 294,000 infants and killed six others.

A report in Chengdu Business Daily said that the leather-powder contamination was first reported to China's quality watchdog in an anonymous letter in February.

In March, local quality inspectors tested samples from eight batches of the dairy products produced by the Morning Garden dairy based in Jinhua City. They found traces of the hydrolyzed leather protein in five batches.

Another inspection of six batches of dairy products on April 2 showed the contaminant was still present in dairy products that the firm was selling to three other cities.

Three people have been detained over the incident.

Leather protein powder is produced from hydrolyzed leather scraps in tanneries. Two compounds contained in leather protein powder – potassium dichromate and sodium dichromate – cannot be absorbed by the human digestive system. Ingesting large amounts of the compounds can lead to swollen joints or even death in children.