Deputy Governor Dimitris Petrovich informed the national broadcaster ERT on Sunday that the wildfire currently blazing in the northeastern Greek region of Evros is unlikely to be effectively contained.
The fire near the city of Alexandroupolis has been raging for nine days.
The European Commission said the blaze, which threatens Greece’s Dadia national park, is the largest single fire in the history of the EU.
Major wildfires were also seen on the outskirts of the capital Athens and on the Aegean island of Andros.
Conditions for firefighters remained difficult as of Sunday morning, Petrovich told ERT.
“Unfortunately, we see that the Dadia front cannot be contained and brought under control,” he said.
Petrovich said that winds were expected to shift on Monday, which could cause the flames to spread even further.
Meanwhile, Greek civil defense authorities said that the overall risk of forest fires has decreased compared to last week.
Around 74,000 hectares (182,858 acres) of land has been scorched across northeastern Greece, including 13,000 hectares in the Dadia national park.
Almost 300 firefighters, seven planes and five helicopters were working to put out the blaze in Evros, the fire department said.
Evacuation orders were issued for a village in Evros and another one in neighboring Rodopi.
The fire in northeastern Greece caused 20 out of 21 wildfire-related deaths over the last week.
A major blaze was also raging on the northwestern outskirts of Athens, burning into the Mount Parnitha national park.
The fire department said 260 firefighters, one plane and three helicopters were working in the area.
A third fire broke out on Saturday on the island of Andros in the Cyclades archipelago. Lightning strikes are suspected to be the cause of the blaze.
In total, over 600 firefighters were battling the blazes across Greece.
Greece has been struck with daily fire outbreaks over the past week.
European Union officials have pointed to climate change as the cause of the increased frequency and intensity of wildfires in southern Europe. Last year was the second-worst year for wildfire damage on record after 2017.