Four officials and 10 police officers have been punished for involvement in fraud committed by a prisoner at a prison in Mudanjiang, according to a statement on the official website of the Heilongjiang Provincial Department of Justice in Northeast China on Tuesday.

The justice authority released the statement after media reports covering the prisoner's story attracted public attention. It said the case happened several years ago. It honored the media's supervision and extended its gratitude to the public.

"We have learned a serious lesson from it," and "We have overhauled the prison system in Heilongjiang and perfected management and rules to prevent the reoccurrence of such cases in the future," the statement said.

Prisoner Zhang Junbo used phones to contact people outside prison and giving different reasons, solicited money. He continued defrauding people even though he was under investigation for another fraud case, the media reported.

Zhang was sentenced to life on a kidnapping conviction in 2003 but his jail term was reduced to 20 years in 2006. In 2009, he chatted with a woman surnamed Wang on Fetion, an instant messaging app, and soon developed a romantic relationship.

Between May 2009 and January 2010, Zhang told the woman that he needed money to bribe officials to let him leave prison earlier and gave some other reasons. The woman sent him more than 3.88 million yuan ($617,500).

When creditors urged the woman to repay the money in January 2010, Wang visited the prison and realized that Zhang had deceived her.

Zhang was kept in solitary confinement when he was under investigation for the fraud case, but during that period, between November 2013 and January 2016, he could still use phones and engaged in seven other fraud cases to cheat people out of more than 700,000 yuan.

At least five officers at Mudanjiang prison favored the money transfer and illegal lottery purchase by providing their bank accounts to Zhang, but the prison did not explain why Zhang could use mobile phones in jail, which is banned by law.