More than 100,000 salted duck eggs suspected of being processed with potentially poisonous industrial salt were found at a workshop in Jiangmen, Guangdong province, last week.Three workers were making salted eggs with industrial salt, according to investigators, in an apartment in a residential community in Jiangmen. Investigators also found 2 metric tons of industrial salt and 52,500 unprocessed eggs stored there, Jiangmen Daily reported.

The investigators seized the goods and are testing the processed eggs.

They are also trying to track down 50,000 salted eggs the boss said he had sold to agricultural produce markets in Jiangmen.

However, that may prove difficult because most salted eggs sold at markets are unpacked and bear no brand label or production lot number, said Shi Chengtie of the quality and technology supervision bureau of Jiangmen.

Industrial salt costs about 800 yuan ($127) per ton, according to the boss, who also operated a salted egg wholesale store in the community and is under investigation. Salt meant for consumption, in contrast, sells for up to 1,400 yuan per ton. according to investigators. It remains as yet unknown how he acquired industrial salt, which is sold only to properly licensed industrial businesses, said Liu Lijie, an official with the salt bureau of Jiangmen.

The three workers said they were not aware that they were using industrial salt or that industrial salt is prohibited in food processing. They said that they occasionally ate the salted eggs they made.

Industrial salt contains poisonous nitrite and may have harmful substances such as lead and arsenic, according to the website of Guangdong Salt Industry.

Eating industrial salt can cause dizziness, headache, fatigue, difficult breathing, vomiting, diarrhea and even death.

“I always buy unpacked salted eggs in small stores. Now I guess it would be safer to buy packaged ones in supermarkets,” said a woman named Zhang in Guangzhou.

In 2006, eggs processed with industrial salt containing a large amount of barium killed two people and poisoned more than 20 others in Jiangxi province. Food cooked with industrial salt sold at a delicatessen in Shanghai killed one person and poisoned 25 others in 2009.

In Guangdong this year, industrial salt was found to be used in soy sauce in Foshan, salted eggs in Dongguan, cooked meat in Guangzhou and preserved vegetables in Huizhou.

Workshops in Beijing, Yinchuan in the Ningxia Hui autonomous region and Leshan in Sichuan province, were found this year to package industrial salt in edible salt bags for sale, according to media reports.