McNuggets sold at a McDonald's outlet in China. A CNN report said chicken McNuggets served in the US contain tBHQ, or tertiary butylhydroquinone, a petroleum-based product, and dimethylpolysiloxane, an anti-foaming agent also used in Silly Putty.

Chinese consumers' concern over the safety of fast food is growing as watchdogs began to inspect McDonald's chicken nuggets, which are reported to contain "two harmful chemical ingredients," with the official conclusion yet to be drawn.

The State Food and Drug Administration is working with relevant departments to monitor McDonald's McNuggets and other products that may contain the additives, the agency said in a statement posted on its website Tuesday.

A CNN report said chicken McNuggets served in the US contain tBHQ, or tertiary butylhydroquinone, a petroleum-based product, and dimethylpolysiloxane, an anti-foaming agent also used in Silly Putty. One gram of tBHQ could cause "nausea, vomiting, ringing in the ears, delirium, a sense of suffocation, and collapse," it said.

The report aroused public fears over the safety of McNuggets sold in China and calls for an official investigation.

An unnamed official with the Ministry of Health in charge of food safety told the Xinhua News Agency Wednesday that the two chemicals are food additives allowed by the Codex Alimentarius Commission, which was created in 1963 by the Food and Agriculture Organization of the United Nations and the World Trade Organization to develop food standards.

Experts with the SFDA said Tuesday that the two chemicals are also on China's additives list, but they still need to determine if the exact dosage of the additives in McNuggets are in line with national standards.

According to China's food additive standards, tBHQ can be used in fat and oil products and fried food with a maximum of 0.2 grams per kilogram, and dimethylpolysiloxane can be used in the processing of edible fat and meat products.

The maximum allowable amounts are 10 milligrams per kilogram and 0.2 grams per kilogram for the two products, respectively.

The SFDA launched an inspection into food safety in 2009, and no food product had been found with tBHQ over the national standard in the 930 batches of sampled edible oil.

Guo Zixia, the vice director of the Beijing Municipal Institute of Health Inspection (BIHI), was quoted by Beijing News as saying that the agency has launched a special inspection of the two additives in McDonald's nuggets, which are not covered in their normal testing of the product.

Chen Min, deputy dean of the Nutrition and Food Security Department of China Agriculture University, said there are thousands of food additives now used, which makes it impossible to inspect every single ingredient or additive.

However, Fan Zhihong, an associate professor at the College of Food Science & Nutritional Engineering at the University, argued that even if the dosages of additives are in line with standards, it's unhealthy to eat too much fried food.

"You will pay the price for the convenience of fast food, as many hazardous substances are produced in the deep-frying process," she said. "The harm of over-used food additives is only a very small part of the overall detrimental effects of fried food."