The fire broke out on Tuesday afternoon in Biłgoraj County, Lublin region.
During the operation, a firefighting aircraft crashed, killing its pilot.
Deputy Interior Minister Wiesław Leśniakiewicz said on Friday that while weather conditions had improved, operations were far from over.
"Every spot must be penetrated by firefighters, checked and flooded with water," he said.
A drone survey carried out on Friday morning identified persistent hotspots, particularly in peat areas in the southern section of the fire zone – the most challenging part of the operation.
Firefighters warned that underground root systems had burned through, making trees liable to fall.
The operation has been divided into five sectors.
The southern one remains the most difficult, while the area near the town of Józefów is the most contained.
A water supply network is being built along the eastern sector as a precaution against changing wind conditions.
Helicopters have been grounded due to low cloud cover, with drones currently being used to monitor ground temperatures.
More than 800 firefighters and 213 vehicles have been deployed.
The fire has burned through an estimated 300 hectares, with operational activity covering around 1,000 hectares.
The Solska Forest is home to several nature reserves, landscape parks and Natura 2000 protected areas.
(ał)
Source: PAP