A headline in Global Times, which is owned by People’s Daily, suggested that winning public trust over the case would be an uphill battle. “Police struggle to convince public of proper conduct of investigation over man’s death,” it read.

The case has overtones of a scandal in 2003, when Sun Zhigang, a recent college graduate who had arrived in Guangzhou for a job as a designer in a garment factory, was beaten to death in police custody in Guangdong Province after being detained for not having a valid residence card. His death set off nationwide outrage and led to the revision of regulations controlling the movement of migrant workers.

Demands for answers as to how Mr. Lei died continued to mount on Thursday, with four strongly worded petitions, said to be from different groups of alumni from Renmin University, circulating on social media. Some links were being deleted by censors.

The authenticity of the petitions could not be independently confirmed, but Beijing News said it had confirmed one, reportedly written by graduates from the class of 1988.

The petition was titled: “We Must Speak Out — Statement by Some 1988 Alumni of Renmin University of China on Fellow Student Lei Yang’s Death.”

It demanded greater rights for Chinese citizens and justice for Mr. Lei, whose family has requested an independent autopsy. The results will take about a month, news reports said.

Here are translated excerpts from the petition, which appeared on a Baidu website on Thursday but was deleted later in the day: