Firefighters in Ukraine are battling to extinguish two forest fires in the exclusion zone around the Chernobyl nuclear power station that have brought a spike in radiation levels since they broke out on Saturday.

More than 100 firefighters, backed by aircraft and other equipment, are trying to contain the fires after working into the night on Sunday.

Authorities said the flames spread across an area of around 100 hectares, inside the 2.600-square-kilometers exclusion zone established after the 1986 disaster. Then, an explosion sent a cloud of radioactive fallout over much of Europe in what is still the world’s worst ever nuclear accident.

“There is bad news: radioactivity is higher than normal at the heart of the blaze,” the head of the country’s environmental inspection service, Yehor Firsov, said on Facebook. He posted a video showing a Geiger counter displaying a level of radioactivity 16 times above normal.

Read more: Euronews