An investigation by China's top judicial body has uncovered more than 13,961 prisoners who have had their jail terms illegally reduced in the past four months by corrupt prison officers.
The Supreme People's Prosecutors' Office made the discovery during a study of the country's prison system, which also found another 3,875 prisoners were released on parole or received medical treatment while on bail.
The SPP said 42 law enforcement officers have been found guilty of reducing prison terms.
An investigation was launched based on suspicions guards were accepting bribes in exchange for shortening prisoner's sentences.
The government is forming a plan to fight corruption in the judicial system.
Local judicial departments have been ordered to review all decisions they made leading to the early release of prisoners from May to September this year.
But the SPP official said in some regions the review was only carried out on paper, without any real attempt to uncover corruption.
Any irregularities in prison terms uncovered during the review would be rectified, and the law enforcement officers found guilty of corruption would be punished.