Two Shenzhen police officers have been jailed for 10 years and at least 13 other people imprisoned over a deadly riot at a detention centre two years ago. The Shenzhen Intermediate People's Court handed down the prison terms to the centre's former head of security, identified by his surname Xie, and an assistant, surnamed Li, for ordering 13 detainees to beat 15 other inmates on January 13, 2004, killing one of the participants and critically injuring several others. The court said Xie and Li ordered the beatings, and the assaults continued throughout the day, with the assailants singing to drown out the victims' cries. One detainee died late that night. The court did not say why the officers ordered the violence. One of the attackers was set free soon after the assaults and later arrested for drug dealing. He was sentenced to 12 years in prison for the beatings and drug offences. The court did not provide details of the sentences handed to the other defendants, who were all inmates in the detention centre at the time of the incident. The sentences came two days after the Ministry of Justice issued a decree reiterating a ban on prison staff and police officers inciting violence against prisoners. The ministry said officers involved in the assault or torture of detainees could lose their jobs or face more severe punishment. The ban also specified several prohibited activities for officers, including asking prisoners for money or property. Fan Fangping, a vice-minister of justice, said the decree was meant to deal with the 'violations which happen most frequently' in the penal system.