BEIJING (AP) -- China's quality watchdog said Wednesday it is investigating the safety of an unapproved protein additive in a premium line of milk produced by one of the country's biggest dairies.
So far, there is no evidence that the substance is dangerous and there have not been any reports of illness, but the action underscores the government's recurring difficulties in policing the manufacturing of products.
The problem was highlighted most recently when infant formula tainted with the industrial chemical melamine sickened nearly 300,000 Chinese babies and was blamed in the deaths of at least six infants.
In a notice posted late Wednesday on its Web site, the General Administration of Quality Supervision, Inspection and Quarantine said it was researching the additive called OMP, a milk protein added by the Mengniu Dairy Group Co. to its Telunsu line. It said results would be published at a later date.
A Mengniu statement released Wednesday said OMP -- or osteoblast milk protein -- helps with the absorption of calcium and promotes bone growth. It is commonly used in other countries under the name "Milk Basic Protein" or MBP, Mengniu said.
"The safety of MBP has been recognized by authoritative international organizations," the statement said without giving more details.
Mengniu spokeswoman Zhao Yuanhua said the statement was issued in response to a report Wednesday by Hexun.com, a Chinese business news Web site, on the presence of OMP and IGF-1, a growth hormone, in the Telunsu line. The statement also said that IGF-1 naturally occurred in milk and was not present in unusually high levels in Telunsu.
China has been trying to monitor the overall usage of additives in food products. In December, the Ministry of Health released a list of substances banned from being added to food. They included chemicals used in industrial dyes, insecticides and drain cleaners. OMP and IGF-1 are not on the list nor are they on a list of approved additives.
Hexun.com said China's quality watchdog sent a letter to Mengniu earlier this month asking it to prove the safety of the two substances. It is unclear what prompted the investigation.
Zhao referred all other questions to the office of Mengiu's chairman of the board, where telephones rang unanswered.
In China, food scares have included the use of the banned cancer-causing industrial dye Sudan Red to color egg yolks. Boric acid, commonly used as an insecticide, is mixed with noodles and meatballs to increase elasticity. Industrial formaldehyde and lye, used in making soap and drain cleaner, is added to water used to soak some types of dried seafood to make the products appear fresher and bigger.
"Any substance intentionally added to food, for technological or other purposes, needs to be evaluated for its human safety," said Dr. Angelika Tritscher of the World Health Organization's Department of Food Safety, Zoonoses and Foodborne Diseases. "It's totally unacceptable to add anything to food without proper testing first."
Tritscher said she had not heard about the protein substance OMP but said that the growth hormone IGF-1 was harmless if taken orally.
The recurring problems indicate that a lax inspection regime still exists, despite repeated promises by the central government to step up product safety monitoring.
Last year's milk scandal, where nitrogen-rich melamine was added to milk to fool protein tests, also exposed loose controls over large companies like Mengniu and Yili Industrial Group Co., whose products were recalled.
Both were exempt from government inspections under waivers given to companies deemed to have proper quality controls. Those waivers were scrapped after the scandal erupted.