Police on the 1st booked four people, including workers and those in charge, on suspicion of occupational negligence causing a fire in connection with the blaze that occurred at the Daejeon headquarters of the National Information Resources Service (NIRS).
Police questioned 12 people, including construction workers, as references through the previous day and then booked three of them. The one NIRS official booked alongside them is site management staff and is not the safety management supervisor, according to reports.
Police said, "There are difficulties in questioning NIRS officials as references as it overlaps with the recovery situation," and added, "We booked four people whom we determined had charges based on statements from construction officials and the materials we secured."
According to police, the fire broke out during the process of separating lithium-ion batteries on the fifth floor of NIRS from servers and transferring them to the basement. NIRS said that before the transfer work, it shut off power to the batteries and cut the cables, and that the fire broke out 40 minutes after the power was shut off.
Police confirmed that a total of 25 closed-circuit (CC)TV cameras were installed inside and outside the computer room and secured the footage, and plan to investigate based on the results of the on-site forensics.
The six lithium-ion batteries believed to have initially ignited have all now been moved to the National Forensic Service. Residual current was detected in one of them, and the National Forensic Service plans to conduct detailed forensics after stabilization.
A police official said, "The statements of the references are consistent and we also checked the log records, and it appears the main battery power breakers were switched off before the work," and added, "However, because there are multiple related breakers, the exact work sequence and cause of the fire will only be known after further investigation and forensic results."