Police are hunting three suspects for dying steamed buns with artificial coloring in east China's Wenzhou City, Zhejiang Province, after authorities closed an unlicensed steamed bun workshop they had worked in for producing food which contain prohibited chemicals.

Officials found synthetic lemon yellow dye being added to unfinished steamed buns during a raid on the workshop on April 15. The dye was previously banned in baking fermentable food, according to the national food production standards. The owner and workers of the workshop, however, were not found during the raid.

Police nailed down three suspects who were involved as the investigation progressed and began to hunt the three who remained at large.

The raid in Wenzhou came on the heels of the shutdown of a Shanghai-based company earlier last the week.

Five managers of Shanghai Shenglu Food Co. are being held by police for adding similar chemical dyes to steamed buns.

The coloring was used to make wheat buns look like corn flour buns so the fake "corn flour buns" could be sold at higher prices, food safety officials said.

Health experts say consuming food with synthetic lemon yellow dye over a long period can cause damage to the human liver and nervous system.

Food safety watchdog said Sunday the workshop in Wenzhou was suspected of producing thousands of steamed buns containing illegal yellow coloring every day for the past two months. Some of the tainted steamed buns, a popular Chinese staple, were supplied to a local school.

The authorities added that they are checking which school the buns were sent to and whether any students became sick after eating the buns.