There have been several cases in the past, wherein people have lost lives in the engine room not because of the fire but because of suffocation after CO2 was released in the engine room.
Suffocation of the crew combined with re-ignition of fire due to lack of air tight engine room has resulted in gruesome condition, as the CO2 system is the last resort for fighting fire and no more firefighting method is available after using that (CO2 system can be used only once).