The eggs, which bounce after being boiled, have been appearing in "small numbers" and are suspected to be fake due to them being too hard to eat.
"The investigation is designed to appease consumers' concerns, after some suspected they bought artificial eggs made by unconscientious traders seeking profits," the Xinhua news agency said.
However, it has been suggested that the hardness of the eggs could be a natural occurrence caused by hens consuming large amounts of food enriched with gossypol.
The compound is known to bind protein in egg yolks and has allegedly been tested for use in male contraceptive pills.
"While gossypol normally exists in the residue of cotton seeds added to chicken feed as an extra protein source, large doses of the compound will suppress sperm activity," the agency claimed.
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