According to a statement from the Zhejiang Provincial Administration for Industry and Commerce, the quality regulator for Zhenjiang province, excessive amounts of nitrite were found in edible bird's nests in the province.
The watchdog added that the tested cubilose (another name for edible bird's nests) was not locally produced, but imported from Malaysia, and it posed threats to consumers' health in China.
Spot checks on blood-red cubilose, a rare type of edible bird's nests, from 491 dealers in Zhejiang have shown that nitrite levels averaged 4,400 mg per kg, far beyond the allowed cap of 70 mg per kg.
According to the Zheijang regulator, the contamination was caused after dealers used dye on ordinary bird's nests and passed them off as blood-red cubilose on the market, resulting in excessive nitrite levels, which have been linked to cancer risk.
Since the announcement, Beijing Tongrentang Co., a retailer of traditional Chinese medicine, has pulled all edible bird's nests off its shelves. The order was effective at all Tongrentang stores in China and abroad two days after the Zheijang announcement.
The State Food and Drug Administration has yet to make an announcement on these products, and did not respond to requests for comments with regards to this issue.
Edible bird's nests are made of the secretion from the saliva glands of birds, and have been used in soup in China for centuries on the belief in their health benefits. They are the some of the most expensive food products in China, Hong Kong, and even the US, where it can cost up to US$10,000 per kg.
Malaysia is the world's biggest exporter of bird's nests, and 95 per cent of them are sold to China.