The State Post Bureau said on Tuesday that it had opened an investigation into courier giant STO Express over safety-management failures at facilities operating under its brand.

The probe followed a string of safety accidents and repeated inspections that uncovered hidden hazards this year at businesses using the STO Express trademark, trade name, and waybills, the regulator said in a statement on its website.

The bureau stated that STO Express had failed to meet its safety-management obligations and had not implemented unified safety oversight as required by regulations.

It did not specify what penalties the company might face if violations were confirmed.