The cost of producing the fake starch noodles was around 3,000 yuan ($461) a ton while noodles made from real sweet potato will cost more than 5,000 yuan to make, the workers said.

Three executives from the company that was raided on Thursday, including the boss surnamed Luo, were detained by police.

They reportedly told investigators that they learned how to make the fake sweet potato noodles from counterparts in Dongguan.

Guangzhou Daily said the three executives told police that they got their additives and corn from the companies in Dongguan.

The claim led provincial quality authorities to send the teams to inspect the starch noodle producers in Dongguan, where they turned up evidence to support the claims.

An official from Guangdong provincial administration of quality and technology supervision, who insisted on anonymity, pledged that the case will be fully investigated and said the authority will severely punish anyone who has broken the law.

Wang Chunlian, a Guangzhou housewife, said the authorities should introduce concrete measures to enhance the supervision of food production and make sure no more tainted food enters the market.

"Food safety affects all households because ordinary residents do not have the ability to distinguish safe products from tainted ones," Wang told China Daily.