Three former policemen went on trial on Friday in northeast China's Heilongjiang Province for alleged abuse of power and dereliction of duty after three inmates escaped from a prison in Yanshou in the province.

Zhang Gequn, Fan Deyan and Zhang Xiuli were tried at the Songbei District People's Court of Harbin, Heilongjiang's capital.

The Procuratorate of Songbei District alleged that Zhang Gequn, former director of the prison in Yanshou County, acted beyond his power to change the rules and reduce the number of guards on night shift from two to one.

Zhang Xiuli, former deputy director of the Yanshou public security bureau, is suspected of being negligent in inspections. Fan, vice director of the prison, allegedly failed to uncover rule violations by guards, said the procuratorate.

Because of their dereliction of their duties, three inmates, Gao Yulun, Wang Damin and Li Haiwei, escaped from a prison at Yanshou county, about two-hour-drive to the capital city Harbin, in the early morning of Sept 2, 2014, after killing a guard.

The guard, Duan Baoren, violated rules on September 2 of last year by taking inmate Gao Yulun to the interrogation room alone at night and leaving the door open. Gao, who had been awaiting execution for intentional homicide, attacked Duan while two other prisoners rushed out to join him.

The trio fled after killing Duan.

More than 15,000 police officers and a police helicopter were deployed in the hunt for the fugitives. Authorities offered a reward of 150,000 yuan ($24,195) for information leading to their capture. They were tried last month. Both trials are still awaiting verdicts.