Police in South Korea have arrested four people in connection with a fire at a government data center that took down hundreds of government services.

The Daejeon Metropolitan Police Agency is investigating whether professional negligence led to the fire at the National Information Resources Service (NIRS) in Daejeon on Friday. The arrested quartet includes NIRS workers and a site supervisor.

Friday’s blaze started in a server room on the fifth floor of the data center. A battery caught fire, destroying 384 battery packs and 740 pieces of IT equipment.

The incident impacted 647 government services, ministers said on Monday, and only 73 of these services have thus far been restored. Bringing the others online could take up to a month.

NIRS provides 1,600 systems as part of South Korea’s e-government service for citizens, as well as acting as an IT services provider for local and national government agencies. Its systems reportedly operate from three data centers, with the Daejeon site providing a third of capacity.

Systems that went offline simultaneously after the fire included the 119 emergency call service, as well as online postal services and government email servers.

Efforts to discover the cause of the blaze and bring servers back online were hampered on Wednesday when a vehicle caught fire in the data center parking lot. Eleven crews were dispatched to the scene and brought the fire under control in 13 minutes. No one was injured.