The General Administration of Quality Supervision, Inspection and Quarantine ordered its local branches on Friday to increase their scrutiny of fresh milk in response to public concerns.

The administration said in a statement posted on its website that it had paid closer attention to the quality of dairy products and increased the frequency of food inspections following a 2008 scandal in which the poisonous substance melamine was found in infant formula.

Since 2009, the administration has placed both melamine and hydrolyzed leather protein - substances that could make food appear to have a higher protein content - on a list of banned additives that must be tested for in fresh milk.

Later that year, the administration punished a company in Zhejiang province after finding the company had added hydrolyzed leather protein to its dairy products.

Even with those achievements suggesting the government has got closer to its goal, Friday's statement indicated that the supervision of fresh milk will be further strengthened in the future.

Li Yuanping, a spokesperson for the administration, said anyone who has concerns about the quality of a food product should call the General Administration of Quality Supervision, Inspection and Quarantine on the hotline number 12365.

The statement came a day after China's Ministry of Agriculture said that fresh milk on the Chinese market is "generally safe" and that no hydrolyzed leather protein or other prohibited materials had been detected in recent tests of that product.

In 2008, milk powder tainted by melamine killed at least six infants and sickened 300,000 children across the country.

Melamine and hydrolyzed leather protein are used as additives because they can make dairy products that have been watered down appear to contain normal amounts of protein.

In a notice posted to the website of the State Council, China's Cabinet, the Ministry of Agriculture said authorities will carry out 6,450 random checks of fresh milk this year - underscoring officials' concerns that dairy producers may still be trying to use illegal and dangerous methods to boost the protein content of milk.

All of the tests will be checks for melamine and 30 percent will be attempts to detect hydrolyzed leather protein.

The agriculture ministry said in a statement posted to its website on Thursday that spot checks performed on 7,406 batches of fresh milk last year yielded no evidence indicating the presence of melamine and signs of leather protein.

The main source of melamine contamination has been powdered milk, rather than the fresh variety. Last year, China seized 2,132 tons of melamine-tainted milk powder, all of it having been manufactured in 2008 or earlier.