BEIJING - Overwork has been the main culprit to blame for the deaths of police officers on duty in the Chinese mainland in the past five years, according to the Ministry of Public Security.

Since 2006, 47 percent of the 2,182 officers who died on duty died from overwork, while those who work in the front lines of law enforcement, such as traffic officers and officers at local police stations, suffered the greatest number of sudden deaths.

"The Labor Law mandates an 8-hour work day, but police officers work much longer," Dai Peng, dean of the investigation department of the Beijing-based Chinese People's Public Security University, told China Daily on Monday. "It's especially true of those who work in the front lines and are subject to prolonged intensive stresses that have seriously affected their physical and psychological health."