'After you read this announcement, please return to the company immediately. We will arrange a medical examination for occupational disease for you at hospital,' it said.

The announcement apparently was in response to recent local media reports and concerns expressed by the Guangdong Women's Federation that workers in the province's shoe factories might have fallen victim to benzene poisoning.

Benzene is commonly used in shoe-making in developing countries but it has been found to be toxic to humans.

It was not immediately clear how many workers were affected, but yesterday's announcement identified 40 workers who might have been exposed to the benzene.

Shoe factories like Anjia are common in Guangdong and many employ hundreds of young women - most of them from outside the province.

China passed a law on May 1 offering greater protection to workers. Under the law, employers are held accountable for workplace safety and are legally bound to provide financial support and treatment to those who suffer from work-related diseases and injuries.

The shoe company has located some of the workers and arranged for their return to Guangdong for treatment. On Sunday, Guangdong's newspapers reported that one of the workers, Tang Wenyan from Guizhou province, had to be carried off an aircraft as her legs were paralysed.

Economist Wang Lian, from Shenzhen University, said the new law was important but local protectionism could still hamper efforts to help workers. He feared local officials would still put profits ahead of workers' benefits.