Apple supplier Foxconn has been forced to shut down its Taiyuan factory in China after a riot involving 2,000 workers broke out late last night.
According to state news agency Xinhua, after 5,000 police officers were drafted in, the fight was brought under control this morning. However, some 40 staff needed medical attention at a local hospital.
Photos are circulating on Twitter, Weibo and othr social media sites showing broken windows and overturned cars.
A spokesperson for the company told Reuters: "The cause of this dispute is under investigation by local authorities and we are working closely with them in this process, but it appears not to have been work-related."
However, other local reports have indicated that the fight broke out after a security guard beat up an employee.
The Taiyuan plant employs about 79,000 staff and is believed to make parts for Apple's iPhone 5, as well as automobile electric components.
Foxconn's become notorious over the last couple of years for poor working conditions. Just last week, human rights organisation Sacom reported that another undercover investigation had discovered that working conditions at the company's Zhengzhou plant were still extremely poor, and management practices 'inhumane'.
"Workers need to acquire an 'off-duty permit' for a toilet break; this is inhumane and unreasonable," says Sacom.
"A worker who did not sit properly in a standard position was asked to write a confession statement, repeating a longstanding unacceptable practice by Foxconn."