SHANGHAI - The food production license held by a company accused of producing tainted steamed buns has been revoked and five suspects -- including the company's director -- have been detained, according to local authorities.

A law enforcement official seals packages of impounded steamed buns on Tuesday at a production facility belonging to the Shanghai Shenglu Food Company, which allegedly used an illegal color additive to dye buns. [Photo/Xinhua]

Shanghai's public security, industrial and commerce, and food safety supervision departments are working together to investigate the allegations against the company, which emerged in an investigative report by China Central Television (CCTV) on Monday.

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CCTV claimed the company had produced steamed buns, or mantou in Chinese, from stale buns that had been returned from local retailers. The company allegedly added illegal chemicals to the expired buns to make them appear fresh.

The Shanghai quality and technical supervision bureau announced on Wednesday that it had revoked the food production license of Shanghai Shenglu Food Company after it found illegal chemicals in tested samples.

The bureau said it tested 19 batches of steamed buns from the company and found that four contained a yellow coloring that is forbidden in steamed food and confectionery. It said it also found sodium cyclamate, an artificial sweetener, in two batches in quantities that exceeded national standards.

According to the Shanghai public security bureau, related evidence has been collected, including chemical additives and the company's production and sales records.

The company's director, Ye Weilu, its sales manager, Xu Jianming, and three staff members have been detained.

The bureau said the company, registered in Songjiang district's Tianma Development Zone, mainly produced steamed buns and flour confectionery. The company had eight workers and an annual turnover of 1.8 million yuan ($275,000), of which steamed buns accounted for up to two-thirds.

The five suspects acknowledged that the company had produced 84,000 packs (with four buns to a pack) since January. The buns were shipped to 10 supermarket chains in the city, including Dia, Hualian and Lianhua.

The bureau said its investigation is continuing.

According to the Shanghai administration for industry and commerce, more than 32,000 steamed buns have been taken off the shelves at supermarkets and impounded by the administration.

The administration ordered local stores and supermarkets to check steamed buns from other manufacturers and stop selling them if they have any doubts about their quality.

Officials from the bureau said it will also carry out tests on other brands supplying steamed food as part of the investigation.

Li Yuanping, a spokesman for the General Administration of Quality Supervision, Inspection and Quarantine, China's top quality watchdog, said it has ordered the quality supervision authority in Shanghai to thoroughly investigate the case and severely punish those responsible for any wrongdoing.

"We must gravely crack down on illegal activities and will never relent," Li was quoted as saying by Xinhua News Agency.