The probe was centred on an Apple manufacturing plant
A Chinese man suspected of stealing a prototype for the fourth generation iPhone has committed suicide.
Before his death, Sun Danyong told friends he had been beaten up by security staff from his firm, Foxconn, one of Apple's largest manufacturers.
Foxconn, a large Taiwanese company which employed Sun in its huge Shenzhen factory, has launched an investigation.
Apple says it is saddened by the death and is waiting for the results of the investigation.
"We require our suppliers to treat all workers with dignity and respect," Jill Tan, an Apple spokeswoman in Hong Kong, told reporters.
Sun Danyong was 25 when he threw himself off a 12-storey building last week.
As part of his job, he was responsible for shipping iPhone prototypes to Apple.
Such prototypes are a closely guarded secret, as Apple likes to keep its new products and upgrades under wraps until their launch date, to heighten customer anticipation.
On 13 July, Sun reported that he was missing one of the 16 units in his possession.
The company immediately launched an investigation into the disappearance; three days later he had jumped to his death.
Sun's former classmates have told Chinese newspapers that during the firm's investigation he was beaten, his house was searched and he was locked up alone in a room.
A local newspaper showed CCTV footage of Sun the day before he died
They say he described what happened in an online chat with them as one of the most humiliating experiences of his life.
Foxconn and the local public security bureau are investigating the allegations, and the firm has expressed its condolences to Sun's family and set up extra counselling services for employees.
It has also has suspended its chief of security, Gu Qinming.
Mr Gu denies hitting Sun, and a CCTV image of the worker on the day before he died - which was featured on the front page of the local Nanfang Metropolitan Daily on Wednesday - appears to back up Mr Gu's version of events.
According to a BBC correspondent in Beijing, Chris Hogg, Foxconn has faced allegations in the past that it treats its employees poorly.
It has always denied such claims, and was cleared by Apple of any serious abuses, our correspondent says.