Firefighters battling Belgium’s largest modern-day wildfire were counting on crucial air support on Sunday to help tame the blaze in a hard-to-access nature reserve, after it doubled in size over the previous 24 hours.

More than 250 firefighters and emergency personnel were mobilised through the night, according to a Sunday morning update from the regional government which warned conditions in the High Fens park near the German border “remain challenging”.

From 80 hectares burned on Friday, the day the fire broke out for reasons still unknown, the area affected jumped to 850 Saturday morning – and by early Sunday had spread to 3,000 hectares (7,500 acres), authorities said.

The blaze broke out in an area of fragile peatlands and pine forests that was ravaged by massive wildfires in 1911, during a similar period of heatwaves and drought – and is the country’s largest wildfire since then.

The entire area near the German border has been blanketed by a thick plume of yellowish smoke, prompting the evacuation of residents from parts of two villages close to the fire.

No homes have been damaged so far, but the blaze remains out of control.