Shanghai police have identified risks in the handling of toxic chemicals in more than 300 laboratories based in colleges and medical and research intuitions, Shanghai Morning Post reported on Thursday.

Police investigations revealed that many laboratory workers purchased and stored highly toxic chemicals without authorization, and that chemical residues were not disposed of properly or in a timely manner.

The police investigation into laboratory practices was launched after Huang Yang, a graduate student at Fudan University in Shanghai, died of poisoning on April 16.

Police claim that Huang's roommate, surnamed Lin, put a toxic substance from a laboratory in their dormitory's water cooler.