A mushroom factory which produced about 35 tons of golden needle mushrooms using a potentially poisonous citric acid has been shut down, Strait News reports.

Some 630 bags of processed mushrooms and 60 buckets being processed were found in the workshop in Gutian county in East China's Fujian province.

Investigators also found 22 bags of industrial citric acid, weighing 25 kilograms per bag. The bags have no characters of food additives printed on them.

The mushrooms were being prepared to be sold to some food-processing factories in Fuzhou, East China's Fujian province, the boss of the workshop reportedly said.

The chemical residue from the citric acid could have adverse affects on the nervous system, induce hypersensitivity and even cancer, according to a chemist.

The administration for industry and commerce in Gutian county charged the workshop for having no food production license, poor sanitary conditions and illegal use of non-food additives.

Golden needle mushrooms are immersed in citric acid in a pool in Gutian county, East China's Fujian province, May 8, 2012. [Photo/CFP]