In one month, four workers have attempted suicide at the Chinese factory Apple hires to make products like the iPad. Why? It's a mystery, but it's also easy to make some educated guesses about what's got workers going nuts.

Here are the four recent incidents outlined by the UK Telegraph, all at Chinese manufacturing contractor Foxconn's large Longhua plant, which makes the recently-released iPad and other products:

  • April 6: An 18-year-old girl named Rao jumped from a factory building. Foxconn claimed she'd been fighting with her boyfriend. A tree broke her fall but she was still severely injured.
  • Mar. 29: A 23-year-old university graduate named Liu jumped from a dormitory window "dressed only in his factory shirt and underwear." He worked in Foxconn's wireless technology department and joined the company in August.
  • Mar. 11: A twentysomething man named Li jumped to his death from another Longhua building; the Chinese press reported his bonus had recently been stolen.
  • Mar.7: A woman named Tian jumped from her dormitory building and injured herself, saying she was "under a great of pressure," in the words of the Telegraph.

For one, there's a culture of secrecy at Foxconn, the company that runs the plant. By all accounts the company is relentless in shielding its work on behalf of Apple's supremely secretive executives. Workers have been interrogated and roughed up, and the company's guards kicked a Reuters correspondent and a New York Times translator was threatened with a beating. Maybe the secrecy and isolation from the outside world — workers live on-suite in dormitories — became too much amid the run-up to delivering the long-awaited iPad. (The iPad was unveiled in late January and briefly handled by reporters, but only under tightly controlled conditions.)

Or maybe the work was too brutal. A sixty-hour workweek is commonplace among Chinese factory workers, and Apple has reported its suppliers routinely violate even this limit. Foxconn was almost certainly under pressure to deliver the iPad quickly and in quantity; Apple had already missed the timeframe publicly announced by CEO Steve Jobs for delivering the tablet computer, albeit narrowly. There was also uncertainty over whether Apple would have enough of the devices to satisfy initial demand, although in the end there were enough devices on hand to approximately match the brisk initial sales of the iPhone.

(Pic: Longhua worker hospitalized during a 2006 food poisoning outbreak. Getty Images.)