About 1,000 companies producing leather goods, shoes and bags in the Guangdong provincial capital have had their business suspended after being suspected of using harmful glues.
Authorities have also sealed up another 31 enterprises and shut down 15 others during an inspection campaign launched at the beginning of this month.
Guangzhou production safety bureau has set up a special task force to investigate enterprises suspected of breaking labor laws relating to health and safety.
"Most of the factories involved were found to have no operation licenses or had violated laws," a bureau official surnamed Wang said on Thursday.
Guangzhou police have also detained six people who are suspected of illegally producing and selling poisonous glues.
The campaign, which has investigated 2,873 companies, was launched after 37 migrant workers who worked in leather, shoe and bag companies in the city's Baiyun and Liwan districts suffered from glue poisoning in November. Four of the workers died.
Liu Yimin, vice-president of Guangzhou No 12 People's Hospital, said his hospital had admitted a further 33 people suffering glue poisoning since then, of whom 28 were still being treated.
Most were in serious condition when they arrived at the hospital, with some put in intensive care units, said Liu.
Their symptoms included headaches, feeling weak overall and incontinence, he added.
"The patients were diagnosed as suffering from acute dichloroethane poisoning, with some of the patients' cerebral and central nervous systems suffering damage," Liu explained.
All the victims, aged between 15 and 50, were migrant workers who worked in the city's small and medium-sized factories producing shoes, bags and leather products and had to use chemical glue.
Statistics from Guangdong provincial bureau of health revealed the number of occupational disease patients has been on the rise since 2003. The province is home to more than 31 million migrant workers from around the country.
In addition to leather, shoe and bag factories, many employees of furniture companies have also been reported with occupational diseases in recent years.
Liu said winter was the peak period for these diseases because most factories closed windows and doors against the cold.
Yang Zhiwei, a lawyer from Guangdong Faquan Law firm, attributed the growing number of work-related disease cases to migrant workers' poor understanding of their legal rights relating to health and safety.
"Government departments should also do more to protect migrant workers' legal interests as they are usually disadvantaged groups, and it is impossible to ask them not to work in the companies with poor working conditions," Yang told China Daily on Thursday.
He urged departments such as police, fire prevention, health, labor, human resources and social security to regularly launch inspections into the operations of local companies.
Chen Xilong, 23, a migrant worker from Central China's Hunan province, said he knew glues could be harmful to health.
"But I have no choice, unless I quit my job," he said.
Liang Qianyun contributed to this story.