Almost 3,000 eggs were removed from a supermarket in the Panyu district of Guangzhou on Monday after a shopper complained the ones he had bought were fake.

Officers from the local industry and commerce bureau have sealed up the eggs in boxes and sent samples to the city branch of the provincial food quality supervision and inspection station.

The results are expected before the weekend.

"If it turns out the eggs were artificially made, the supermarket will be fined between 2,000 yuan ($317) and 50,000 yuan," said Liu Yuming, head of the food section at Panyu administration for industry and commerce.

Mr Yuming revealed that the batch of eggs that contained the suspect ones had come from two wholesale markets in the Baiyun district, Guangzhou.

Officers from Baiyun administration for industry and commerce carried out spot checks on 14 stores in the wholesale markets on Tuesday and have sent samples of the eggs in these stores to China National Analytical Center, Guangzhou.

Zou Yingqiang, head of the food inspection section at Baiyun administration for industry and commerce, added that the 14 stores had bought eggs from suppliers in Guangzhou and other provinces including Hunan, Hubei, Jilin, Liaoning and Chongqing municipality.

A local resident surnamed Guo bought the allegedly fake eggs from a supermarket called Jia De Fu on 30 January. The next day, when his young child suffered a stomach upset after eating one of the eggs, Guo discovered that the boiled yolk was hard to chew or crumble.

According to Zhao Qiangzhong, an associate professor from the school of light industry and foods at South China University of Technology, the eggs Guo bought are likely to be fake, judging by the abnormal size and flexibility of the boiled yolk, which was like a rubber ball. The yolk is smaller than usual and it bounced on the floor three times, he claimed.

Mr Qiangzhong revealed that there are many ways to mix chemicals and make a bogus egg. For example, sodium alginate solution can be used to fake the egg whites and the yolk.

"Sodium alginate is edible but it certainly doesn't contain the nutrition of a real egg," said Mr Qiangzhong. "But if the egg is made from chemicals that are not edible, such as the material used in a bouncy ball, it will harm health."

However, Professor Yang Lin from South China Agricultural University said the eggs might not be artificially made.

"A high proportion of fried cotton seeds in chicken feed may also make a boiled yolk more elastic than usual," said Professor Yang, an expert in animal feeds.

Professor Yang revealed that in order to reduce costs, some farmers increase the proportion of fried cotton seeds in chicken feed from below 6 per cent to over 10 per cent because the seeds are cheaper than soybeans.

But the cotton seeds contain a toxic pigment called gossypol that can inhibit sperm production and has been used in experiments in male contraception.

"The free gossypol contained in fried cotton seeds has minor toxicity and may do harm to animals and human beings," Professor Yang warned.

Meanwhile, Fan Zhihong, associate professor on nutrition and food safety from China Agricultural University, questions whether artificially producing eggs is profitable. For example, she said, it takes very refined techniques to create a rough surface with lots of tiny holes and fake an eggshell.

Mr Zhihong also noted that a small hole in the eggshell can also lead to a hardboiled yolk being hard to chew, because the water had leaked from the hole.

In the past month, suspected fake eggs have been reported in other cities, including Leizhou in Guangdong province and Yantai in Shandong province.