Updated at 12.49pm: Police on Wednesday were conducting an internal inquiry into the death of one of their fellow officers - believed to have shot himself with his own service revolver. A spokesman said the incident occurred at Tse Wan Shan police station on Wednesday morning. The 29-year-old officer, surnamed Yeung, had told his colleagues he was not feeling well and needed to go to the toilet. Officers later found him lying unconscious with a gunshot wound to his head inside a night shift room on the fifth floor of the station, the spokesman said. Yeung, who was a police constable, was immediately rushed to the Queen Elizabeth Hospital. He was certified dead at 6.26am. This is the fifth case in which a police officer has killed himself this year. There is concern in Hong Kong about the high suicide toll among police officers. Last year four cases were recorded. But in 2003, 10 officers committed suicide, including Assistant Commissioner Cheung Chi-shum. He was the most senior Hong Kong police officer to kill himself and the reasons for his death still remain a mystery. The suicide figure was six in 2000, and rose to eight in 2001 and 2002. Past inquiries have often linked police suicides to high levels of stress, debts or family and relationship problems. In April 2004, a 42-year-old detective constable shot and killed himself. An inquiry revealed he was depressed over his mother's death three months earlier. Last August, a 52-year-old constable jumped to death after becoming depressed over debts he had incurred totalling $800,000. Hong Kong has one of the highest suicide rates in the world. A total of 1,264 people killed themselves in 2004, almost 3.5 per day.