BEIJING (AP) — A factory in China owned by the manufacturer of Apple's iPhones resumed production Tuesday after a brawl by workers highlighted tensions that labor groups say were worsened by the pressure of a new iPhone launch.

Foxconn Technology Group and police said the cause of the unrest Sunday night was under investigation, but labor activists said the rollout of the iPhone 5 has led to longer working hours and more pressure on workers. Foxconn and police said as many as 2,000 employees were involved in the brawl and 40 people were reported injured.

The iPhone 5 debuted last week in the United States and eight other countries and Apple has a three- to four-week backlog of online orders. Foxconn has declined to say whether its one-day suspension of production Monday in Taiyuan might affect supplies. It did not respond to a request for comment on the labor groups' claims.

News reports and witnesses said the violence Sunday night in Taiyuan in northern China stemmed from a confrontation between a factory worker and a guard that escalated. One employee reached by telephone said the violence was fueled by workers' anger about mistreatment by Foxconn security guards and managers.

"Foxconn, some supervisors, and security guards never respect us," said the employee, who asked not to be identified by name. "We all have this anger toward them and they (the workers) wanted to destroy things to release this anger."

Production at the Taiyuan factory resumed on Tuesday, Foxconn said in a written statement. It did not respond to a request for information on the status of its investigation or whether policies at the factory might be changed.

Foxconn, owned by Taiwan's Hon Hai Precision Industry Co., is the world's biggest assembler of consumer electronics, with about 1.2 million workers in factories in Taiyuan, the southern city of Shenzhen, in Chengdu in the west and in Zhengzhou in central China. It makes iPhones and iPads for Apple and also assembles products for Microsoft Corp. and Hewlett-Packard Co.

Labor activists say the need to ramp up iPhone 5 production has increased pressure on Foxconn employees.

"Because of the launch of the iPhone 5, the workload of workers suddenly surges," said a Hong Kong group, Students & Scholars Against Corporate Misbehaviour, in a report this month. It said some employees interviewed at the Zhengzhou factory had not had a day off in the previous 30 days.

Foxconn has declined to say which products are made in each factory but another group, China Labor Watch, said the Taiyuan facility, which employs 79,000 people, is making the iPhone 5.

The group, based in New York City, complained that employees suffer "verbal and physical abuse" by guards.

"These workers must be treated with respect," it said in a statement. "And both Apple and Foxconn, with billions of dollars in profits every year, have both a legal and ethical obligation to uphold the rights of these workers."

Labor tensions in China have been aggravated by a slowing economy that is squeezing employers and a communist system that prohibits independent labor unions.

Many factories and other businesses have unions but they must be part of the state-sanctioned All-China Federation of Trade Unions. Workers complain leaders of local branches often are allied with management and fail to stand up for the workforce.

That means grievances over pay or other issues spiral into strikes and protests. In some cases, ACFTU representatives have scuffled with striking workers, trying to force them to return to work.

"They have no other way of voicing their grievances," said Geoffrey Crothall, communications director for China Labour Bulletin, a Hong Kong organization that promotes employee rights in China. "There are no formal channels of communication or ways of resolving grievances through peaceful negotiation."

Foxconn raised minimum pay and promised in March to limit hours after an auditor hired by Apple found Foxconn employees were regularly required to work more than 60 hours a week.

That review followed a rash of suicides at Foxconn facilities — about a dozen since 2010 — and an explosion at the iPad-making plant in Chengdu in May 2011 that killed four employees.

Foxconn's facilities are exceptionally large by the standards of a Chinese electronics industry in which most manufacturers employ hundreds or thousands of workers. Its flagship mainland factory in Shenzhen, near Hong Kong, has 250,000 workers. The Chengdu site has 100,000 and the company has said the Zhengzhou factory might eventually employ 300,000.

Foxconn also has faced criticism in the past over the conduct of its security guards.

In 2010, Foxconn's parent, Hon Hai, pledged its guards would obey the law and refrain from using threats or harassment after a videotape showing several beating workers was circulated on the Internet.

Foxconn employees have complained about what some critics call "military-style management."

"Workers are expected to obey their manager at all times, not to question but simply do what they are told," said Crothall. "That atmosphere is not conducive to a happy or contented workforce. It's a very dehumanizing way of treating workers."

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AP researcher Flora Ji contributed.

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Foxconn Technology Group: www.foxconn.com

China Labor Bulletin: www.clb.org.hk

China Labor Watch: www.chinalaborwatch.org

Students & Scholars Against Corporate Misbehaviour: www.sacom.hk

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    On February 21, <a href="http://www.huffingtonpost.com/2012/02/22/nightline-apple-supplier-foxconn_n_1293393.html?ref=technology" target="_hplink">ABC aired a "Nightline" segment featuring Bill Weir's visit to a Chinese Foxconn factory</a> responsible for making some of Apple's popular devices. During a tour of the factory, Weir says he "expected more robots" but in fact most of the gadgets at Foxconn are made the old-fashioned way: The high tech parts are put together by hand. For example, iPhones are assembled by hand in 141 steps. One iPad takes five days to assemble and passes through 325 sets of hands.

  • Insane Output

    Two shifts of workers toiling in 12 hour shifts can make 300,000 iPad camera modules in one day, not to mention shape sleek iPads out of "raw hunk[s] of aluminum" at a rate of 10,000 per hour. <a href="http://abcnews.go.com/watch/nightline/SH5584743/VD55173552/nightline-221-apples-chinese-factories-exclusive" target="_hplink">Image via Nightline</a>

  • 7 To A Room

    Many workers live at the factory, where they pay $17.50 per month to live 7 to a room in Foxconn dormitories. <a href="http://www.forbes.com/sites/connieguglielmo/2012/02/22/nightline-goes-inside-apple-factories-in-china/" target="_hplink">The average starting salary is $285 per month,</a> and workers must pay for their food. <a href="http://abcnews.go.com/watch/nightline/SH5584743/VD55173552/nightline-221-apples-chinese-factories-exclusive" target="_hplink">Image via Nightline</a>

  • No Free Lunch

    Workers get two hour-long meal breaks during each 12-hour shift. They eat together in a cafeteria where they pay $.70 a meal. This is about a quarter of their hourly wage. <a href="http://abcnews.go.com/watch/nightline/SH5584743/VD55173552/nightline-221-apples-chinese-factories-exclusive" target="_hplink">Image via Nightline</a>

  • Tim Cook Investigated Suicides

    In 2010, after a spate of suicides at Foxconn's Shenzen plant, then COO Tim Cook flew to China to investigate the matter. <a href="http://abcnews.go.com/watch/nightline/SH5584743/VD55173552/nightline-221-apples-chinese-factories-exclusive" target="_hplink">According to Nightline,</a> Cook put together a team of psychiatric experts to examine the issue. It was at that team's suggestion that the infamous nets were installed between the buildings to prevent suicides. There have been 18 worker suicides at Foxconn since 2010. <a href="http://www.reuters.com/article/2012/02/15/us-china-apple-idUSTRE81E1FQ20120215" target="_hplink">According to Reuters' interview with Fair Labor Association president Auret van Heerden, the group's initial findings from its audit of Foxconn</a> suggested that the suicides could have been "a function of monotony, of boredom, of alienation perhaps."

  • Young Workers

    Weir said he was surprised to see how young the workers were. He said many were in their late teens and no one looked like they could be over 30. Many had left their hometowns, oftentimes in the countryside, in order to get jobs at Foxconn. Weir also toured Chengdu and spoke with the relatives of workers who had left for jobs at Foxconn. According to Cult of Mac, <a href="http://www.cultofmac.com/147878/foxconn-employees-say-underage-workers-were-hidden-before-fla-inspection/" target="_hplink">Foxconn may have hidden underage employees</a> when the Fair Labor Association conducted its inspections. While Apple allows for workers as young as sixteen to assemble their products, those eighteen and under are afforded "special protections," <a href="http://www.appleinsider.com/articles/12/02/22/factory_workers_claim_foxconn_hid_under_age_employees_before_fla_inspection.html" target="_hplink">according to Apple Insider.</a> These include not being allowed to perform some tasks and working shorter hours than older workers.

  • Foxconn Exec Wants To Pay More

    When asked how Foxconn would react if Apple suggested doubling workers' pay, Foxconn executive Louis Woo told Weir that the company would welcome a raise for employees. "Why not?" Woo said. "That would be good for the employees and also definitely good for China and good for us."

  • Air Showers

    Workers have to wear static-proof jackets and take "air showers" to make sure the work area remains dust-free. Even one spec of dust could prove ruinous to the iGadgets' delicate innards. <a href="http://abcnews.go.com/watch/nightline/SH5584743/VD55173552/nightline-221-apples-chinese-factories-exclusive" target="_hplink">Image via Nightline</a>

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