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. [Special coverage]

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In a high-profile case in November, an inmate escaped from Beijiang Prison by exploiting management flaws and outdated facilities, according to the Ministry of Justice.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

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.