Fire crews at the Biebrzański park in the country's north-east were being supported by the army and by special firefighting planes, public broadcaster Polish Radio’s IAR news agency reported.
Fire brigade spokesman Krzysztof Batorski said the situation was under control, but added there were places where the blaze could break out again.
The fire, which started on Sunday, has swept through 6,000 hectares of the park, the IAR news agency reported.
It added that the blaze was caused by illegal grass burning, a common practice in Poland by people who want to clear their land.
Interior Minister Mariusz Kamiński said on Wednesday that two police helicopters, a Black Hawk and a Bell, would support firefighters’ efforts from the air.
Kamiński added that the park is the only site of its kind in Europe.
(pk/gs)
Source: IAR