At least 40 people were injured in a riot at an electronics factory in northern China operated by Taipei-based Foxconn Technology Co., Ltd. (TPE:2354), a supplier for major U.S. tech companies and one of China’s largest employers.

About 2,000 workers were involved in the fighting, which broke out in a privately managed workers dormitory at around 11 p.m. (1500 GMT) Sunday in Taiyuan, Shanxi province, according to Sky News. About 5,000 police were dispatched, and the rioting was brought under control by around 3 a.m. Monday morning. The facility was closed for the day and was expected to be back online Tuesday. The cause of the riot is said to have been "a personal dispute between several employees," said a company statement posted by Sky.

“We want to give people time to cool down,” Louis Woo, spokesman for Taipei-based Foxconn said by phone to Bloomberg.

The Taiwan-based company is a major supplier of iPhone developer Apple Inc. (NASDAQ:AAPL) and employs about 79,000 workers in the facility. Foxconn did not confirm whether any parts of iPhone 5 were made at the factory. The company, which employs about 1.2 million workers in China, also supplies parts for Hewlett-Packard Company (NYSE:HPQ) and Microsoft Corporation (NASDAQ:MSFT).

The cause of the fight was immediately not known, and the authorities have launched an investigation into the incident, said Foxconn.

"We want to give people time to cool down," Louis Woo, spokesman for Foxconn, told Bloomberg, adding that union leaders would be sent to the site to discuss the issue with the workers.

Foxconn had been in the middle of a controversy because of the poor working conditions in its plants.

An independent audit from the U.S. Fair Labor Association, or FLA, revealed long working hours, poor safety standards and delayed overtime payments in Foxconn facilities.

The investigation has found that employees often worked more than 60 hours a week and sometimes for seven days a week without the mandatory one day off. It happened though the Chinese labor law limits the weekly working hours to 49 hours a week.

There was a string of suicides at the Foxconn factories in 2011 that was attributed to poor working conditions in the plants by rights groups and activists.

Foxconn shares fell slightly onn the Taipei Stock Exchange, closing at NT $2.62 (U.S. 9 cents).