Ukrainian firefighters worked overnight trying to put out two forest blazes in the area around the Chernobyl nuclear power station.
The area was evacuated because of radioactive contamination after the 1986 explosion at the plant.
Ukraine’s emergencies service said one of the fires, covering about five hectares, had been localised.
It said the other fire was about 20 hectares.
The head of the state ecological inspection service, Yehor Firsov, earlier said the fires had spread to about 100 hectares.
Mr Firsov said radiation levels at the fire were substantially higher than normal.
But the emergencies service said radiation levels in the capital of Kyiv, about 60 miles south, were within norms.
The fires were within the 1,000-square-mile Chernobyl exclusion zone established after the 1986 disaster at the plant that sent a cloud of radioactive fallout over much of Europe.
The zone is largely unpopulated, although about 200 people have remained despite orders to leave.