Isn’t that how the Chernobyl disaster first came to public notice, sky-high radioactivity readings over Western Europe? The uproar and alarm was so great that the USSR finally had to admit to a minor accident . . . Of course it was anything but minor. This event sounds genuinely minor, thank heaven.
Could be radiation from that (nuclear weapons) and conventional (?) bomb fabrication/storage/enrichment/bomb-missile depot that exploded near Tehran a few days ago.