Beijing prosecutors announced Thursday that they have approved the arrest of two police officers involved in the death of Lei Yang for dereliction of duty, after an autopsy found Lei died from choking on his own vomit.

For the past two months, Chinese media has been probing the mysterious death of Lei, a young man who died in police custody during a raid on a foot massage parlor in Beijing's Changping district in May, triggering a public outcry and raising suspicions of police brutality and abuse of official power.

The People's Procuratorate of Beijing Municipality concluded in a statement published on its official website on Thursday that "Lei died from choking on his own vomit."

An officer surnamed Xing, who is the deputy head of Dongxiaokou police station in Changping, and an auxiliary officer surnamed Zhou should take major responsibility for the tragedy and also impeded the investigation after the incident occurred, the statement said.

Based on their behavior, prosecutors approved the arrest of Xing and Zhou for dereliction of duty, it added.

"Accusing police officers of dereliction of duty means that the prosecutors basically thought they did not use an act of force on Lei," Gao Yandong, a professor of criminal law at Zhejiang University, told the Global Times on Thursday.

Dereliction of duty might mean that police did not give Lei timely help when he showed signs of physical discomfort, Gao said.

Wang Jusheng, a forensic doctor from the procuratorate, told China Central Television that under normal conditions, a person will gag and cough intensely if unidentified matter enters his or her respiratory tract. However, when a person is impaired due to conditions such as a brain injury or drunkenness, this gagging and coughing reaction will not occur or is diminshed, allowing any vomit to be inhaled into the respiratory tract.

Wang noted that further investigation is needed to determine why Lei inhaled his vomit.

"Lei was able to walk normally before the police got involved, and he was not drunk, so the suffocation must have been caused by outside violence," Chen Youxi, the lawyer representing Lei's family, said on his Sina Weibo account.

Wang said the identification center entrusted with conducting the autopsy conducted a meticulous, comprehensive and objective inspection. The anatomy inspection portion of the procedure took over 10 hours and involved the inspection of 257 tissue samples, which exceeds the normal workload for an autopsy, he said. Moreover, the center also hired several famous forensic specialists to check the report to guarantee its accuracy, Wang stated.

Wang noted that the autopsy did not exceed the entrustment period of 45 to 60 business days.