Germany’s Office for Radiation Protection reported increased radioactivity in parts of Central and Western Europe last week.
The increased levels were detected across six locations in Germany and several others across Europe including Austria, France, Germany, Italy and Switzerland.
The Office for Radiation Protection said it could not be an accident at a nuclear power plant.
They added: “New analyses on the source of the radioactive substance ruthenium-106 suggest a release in eastern Europe, at a distance of more than 620 miles from Germany.
“New analyses of the source of the radioactive material are likely to indicate a release in the southern Ural.
“But other regions in Southern Russia cannot be excluded.”
The particles are ruthenium-106 which is an isotope used in cancer treatment for eye tumours and also radioisotope thermoelectric generators which power satellites.
The elevated levels do not present a threat to human health and officials say there is no need to panic.
A spike in radiation was also reported in February this year, many believe it could have been Russia conducting secret nuclear testing.
An increase in the radioactive Iodine-131 was first detected over the Russia-Norway border in January, but that spike has since made its way across Europe.
The increase was then noticed in Finland, Poland, Czech Republic, Germany, France and Spain but authorities decided to keep the information private as they believed it “had no news value”, according to the Norwegian Radiation Protection Authority (NRPA).
France’s nuclear safety authority the IRSN added that the spike of Iodine-131 raised “no health concerns” and the levels have since gone back to normal.
Theories have begun to circulate that Russia is testing nuclear weapons in the Arctic circle as Iodine-131 is a radioisotope found in the atomic bombs tested by the US and Russia in the early days of the Cold War.
Swedish website Cornucopia wrote that Iodine-131 “is an isotope that occurs upon detonation of uranium-235 or plutonium-based nuclear weapons”.
It added: “Russia is upgrading its nuclear weapons to the new state of the art robots and it is not unreasonable that, in so doing, to develop new warheads and not just carriers.”