Prosecutors in Guangdong province have conducted a thorough investigation of prisons and have improved their oversight to prevent prison escapes, as well as illegal paroles or commutations of sentences for convicted ex-officials or wealthy individuals, a senior officer from the Guangdong Provincial People's Procuratorate said.

"We have carefully examined all 127 prisons and detention houses to spot safety loopholes and enhance supervision to fight such crimes," said Zheng Hong, chief prosecutor at the procuratorate, who is also a deputy to the National People's Congress.

The investigation found that "backward equipment and management loopholes were mainly to blame for prison breaks", Zheng said.

In addition, some officers at the prisons neglected their duty and abused their powers to help many ex-senior officials or wealthy people secure conditional releases in exchange for bribes, he said.

"We have put forward valuable suggestions to rectify the safety loopholes in the prison system and enhance our supervisory efforts to prevent similar cases in the future," Zheng said.

Since the beginning of last year, a series of incidents involving escaped convicts or illegal commutations occurred in the Guangdong prison system, arousing public and media attention at home and abroad.

In a high-profile case in November, an inmate escaped from Beijiang Prison by exploiting management flaws and outdated facilities, according to the Ministry of Justice.

Vice-Minister Zhang Sujin said that 1,200 meters of the prison's 1,700-meter-long wall didn't meet standards, including a lack of electronic fencing, surveillance equipment and alarms; and there was no video surveillance equipment in the work area.

The police captured the 28-year-old fugitive one kilometer away from the prison 29 hours later, the ministry said.

In a recent bribery case, Huang Ziyi, former senior officer at Guangdong's Shaoguan prison, allegedly abused his power by helping 16 convicts illegally obtain reduced sentences. Huang has been charged, prosecutors said.

Zheng said that most of the inmates whose sentences were illegally commuted, or who were released on parole, were in prison for duty-related crimes, economic crimes or Mafia-style gang crimes.

"Some police officers abused their power to help them accumulate points that contribute to getting a sentence commuted," Zheng said.

In addition, some convicts submitted fake medical certificates to the prison. Certain medical conditions require that sentences be served outside, he said.

Under the Criminal Law, an inmate who behaves well or is credited with "meritorious achievement" is eligible for a reduced sentence or conditional release, said Pi Yijun, a law professor at China University of Political Science and Law.

Convicts diagnosed with serious illnesses, such as cancer, heart disease or high blood pressure, can apply to serve their sentences outside so they can receive medical treatment, he said.

Zheng, the vice-minister, said a careful examination and review will be made of all the documents submitted to the prisons by convicts seeking modifications of jail time. The reviews will take place before court hearings.

"The court will then issue a new judgment in commutation cases to ensure judicial fairness," he said.

In addition, an online database will be created by the province for sharing information between prisons, prosecutors and courts. Supervision of the commutation process will be improved, and punishments for prison authorities' misconduct will be intensified, he said.

Since last year, 59,692 cases involving requests for commutation or conditional release for inmates, or requests to serve jail terms outside, have been reviewed, the authorities said. Of those, 1,524 illegal cases were uncovered and rectified, and 16 police officials have been charged with duty-related crimes.