Recovery operations following a fire at a national data center late Friday will likely take longer than expected as the lithium battery that caught fire has yet to be completely extinguished.

According to Daejeon fire authorities on Saturday, the main flames at the National Information Resources Service(NIRS) were brought under control some ten hours after the fire initially broke out, and work has been underway for more than six hours to vent heat and smoke to allow firefighters to enter the premises.

The thermal runaway, which takes place when a battery cell short circuits and starts to heat up uncontrollably, is reportedly impeding efforts to extinguish the blaze, with the temperature inside the building that has no windows spiked to 160 degrees Celsius at one point.

Authorities turned off all the servers due to the breakdown of temperature and humidity management systems inside the data processing room, resulting in a suspension of 647 of the government's online systems.

The fire started at around 8:20 p.m. Friday following an explosion of a lithium battery inside the center's data processing room while a worker tried to replace the battery.