Dong Hui and Yang Lifei/Shanghai Daily news

Zhabei District police are investigating an armed attack at a sex shop on Tuesday night, which left two staff members injured including one in critical condition after suffering serious knife wounds, Shanghai Daily reported.

Police said they were still looking into the motive for the violence, but it may have resulted from a dispute over sex medicine sold by the shop that allegedly left a customer with physical problems, said Zeng Ni, media coordinator with Zhabei District police. The four assailants are still at large, police said.