France, Aug. 16 -- More than 250 firefighters and emergency personnel worked through the night in the High Fens nature park, where authorities said conditions remained challenging after the affected area more than doubled in the space of 24 hours.

The fire broke out on Friday for reasons that are still unknown, initially burning around 80 hectares. By Saturday morning, the affected area had grown to 850 hectares, before expanding to around 3,000 hectares by early Sunday.

The blaze is the largest recorded in Belgium since 1911, when the same region was hit by major wildfires during a similar period of heat and drought.

A thick plume of yellowish smoke has blanketed the area close to the German border, prompting the evacuation of residen...