From The Guardian:
An earlier post by Firsov had warned about heightened radiation levels at the site of the fire, which he said had been caused by the “barbaric” practice of local grass fires often started in the spring and autumn. “There is bad news – radiation is above normal in the fire’s centre,” Firsov wrote on Sunday.
The post included a video with a Geiger counter showing radiation at 16 times above normal. The fire had spread to about 100 hectares of forest, Firsov wrote.