The ongoing investigation into the death of a 29-year-old Beijing man who was found dead in police custody has seen a new development.

Beijing’s municipal prosecution office said on Thursday that after Lei Yang’s family officially filed for an investigation into the case, the related documents were transferred to the Changping Procuratorate for further review.

The People's Procuratorate of Beijing Municipality said on its official microblog that Lei’s wife filed a request on Tuesday to open an investigation, accusing law enforcement officers from Changping District police bureau of intentional injury, abuse of power and forgery of evidence. The office has reviewed the documents in accordance with the law. Although Changping Procuratorate will be reviewing the documents, the municipal office will still supervise the case.

Lei, who graduated with a master's degree from the prestigious Renmin University, died on the night of May 7, after police raided a foot massage parlor that was alleged to be hosting prostitution. Police claim that Lei had hired a prostitute when they apprehended him.

After his death, Lei’s family raised doubts about the official police story. Their main concern is whether the law enforcement officers involved in Lei's death followed protocol. The case, which is still under investigation, has sparked wide-ranging public outcry.

Beijing Municipal Public Security Bureau stated Thursday that the bureau attaches great importance to this case. It has asked Changping District police to cooperate fully.

Public security organizations will respect the facts and laws, and handle the case in accordance with the law, the office pledged, adding that they “will never cover up the facts.”