Nineteen people are under investigation for a data center fire that took down online government services in September.

The Daejeon Metropolitan Police precinct said Tuesday that it is investigating nine people, including National Information Resources Service (NIRS) President Lee Jae-yong, the on-site manager for the builder, and the chief supervisor, for allegations of occupational negligence in connection with the fire.

The NIRS chief and three other agency officials stand accused of neglecting to fulfill their duties to manage and supervise the enforcement of safety measures during electrical construction.

Police also suspect that 10 other employees of the official contractor and several illegal subcontractors failed to follow occupational health and safety standards, in violation of the Electrical Construction Business Act.

Based on the National Forensic Service's investigation and analysis, the police concluded that the workers' failure to disconnect a considerable number of lithium batteries from the uninterruptible power supply system caused the fire.

The Daejeon police plan to refer the suspects to prosecution once the ongoing investigation is complete.