Two police officers are being investigated over the death of a senior high school student in northwest China's Shaanxi Province, local authorities said Wednesday.

Xu Gengrong, a 19-year-old student at the Danfeng High School in Danfeng County, Shangluo City, who police say had murdered a female high school student, died on the morning of March 8 after an interrogation at the Danfeng County Public Security Bureau, according to a statement issued by the county government.

"During the interrogation at 10:30 a.m. on March 8, Xu Gengrong's face suddenly turned yellow and he also showed symptoms of short breath, feeble pulse and salivating. Police officers immediately sent him to the Danfeng County Hospital, and he died at 11 a.m. after emergency treatment," the statement said.

Wang Qingbao, a senior officer in charge of disciplinary inspection at the county public security bureau, and Sun Peng, head of the criminal police team, are under investigation by the procuratorate authorities for "dereliction of duty," the statement said.

Wang was detained Monday and Sun was guaranteed pending trial Tuesday, it said.

Xu's death has sparked suspicion among residents and netizens about whether he suffered torture during the interrogation, because his relatives said visible wounds had been found on his body in a postmortem held on March 9.

"I saw visible wounds around his wrists, and gores and bumps on his head. Forensic doctors told me those were as a result of diseases or external forces," said Wang Shihong, Xu's uncle told Xinhua.

Wang witnessed the whole of the postmortem, carried out by the Shaanxi Provincial People's Procuratorate and the Shangluo Municipal People's Procuratorate. It was held at the request of Xu's relatives.

Xu's mother dismissed "diseases" as the cause of her son's death.

"My son had been healthy and strong, and he won several awards in sports meeting. So he couldn't have died of diseases. We wonder why he died suddenly without an unclear cause," said Cao Huiling, from the Siping Village of the Siping Township in Danfeng.

"We need an explanation from the government," she said. Xu's relatives have petitioned for an investigation since March 9. No protests of local residents were reported.

The local government has paid 120,000 yuan (17,647 U.S. dollars) for "funeral costs" and "pension" to Xu's his relatives, who accepted the money and buried Xu's body Monday.