"The fight is over now ... we're still investigating the cause of the fight and the number of workers involved," said Foxconn spokesman Louis Woo, adding that it was possible it involved "a couple of thousand workers".
The Taiyuan plant, which employs about 79,000 workers, makes parts for automotive electronics and assembles various electronic devices, according to Woo. Other staff sources said that it makes parts for and assembles Apple's new iPhone 5, released only last week.
Woo said the fight happened in the workers' dormitory facilities and said the company would issue a statement later on Monday. Reports on social networks suggested that the trouble began after a security guard hit one of the workers. They also suggested that a handful of people were hospitalised. Photos posted to social networks but later deleted showed smashed windows and riot police, and crowds of workers.
China's Xinhuanet.com, operated by the Xinhua news agency, said about 10 people were hurt in the fighting, citing police.
Geoffrey Crothall, spokesman for the pressure group China Labor Bulletin, told the New York Times that workers at the plants had become increasingly emboldened.
"They're more willing to stand up for their rights, to stand up to injustice," he said. The same plant was the subject of a brief strike over pay in March.
Foxconn, the trading name of Taiwan's Hon Hai Precision Industry Company, is the world's largest contract maker of electronic goods. It has seen a few violent disputes at its sprawling plants in China, where it employs a total of about 1 million workers. It is an important supplier for companies including Apple, Hewlett-Packard and Microsoft.
By late Monday morning, Hon Hai shares were down 1.14%, lagging the broader market's decline of 0.28%.
In June, about 100 workers went on a rampage at a Chengdu plant in southwestern China. The company has faced allegations of poor conditions and mistreatment of workers at its China operations, and has been spending heavily in recent months to improve the work environment and to raise wages.
A staff member at the Taiyuan plant said he was told the plant could be closed up to two to three days for police investigations.
"There are a lot of police at the site now," said the staff member, who asked not to be named.
Calls to the Taiyuan police were not immediately answered. An official at the plant declined to comment when reached by telephone.
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