Norway’s nuclear safety authority is analyzing a small amount of radioactive iodine detected in the air over the country’s north in the days after a deadly explosion involving a nuclear powered device over the border in Russia

Russia’s state nuclear agency, Rosatom, said Saturday that five people killed in the blast were its staff members and that the accident involved “isotope power sources,” giving no further details.

The mysterious incident, which took place in the Arkhangelsk region, caused radiation levels to briefly rise in Severodvinsk ­– a city of 190,000 – but those reports were squelched by order of Russia’s Ministry of Defense.

Those who were injured in the blast were taken to Moscow for treatment, but have been forbidden by authorities to discuss the details of the mishap.

The lack of clear explanations from Russian authorities has left the international community on edge and news of possible radiation produced jittery international headlines.

On Thursday, Norway’s radiation and nuclear safety authority DSA said it had detected the radioactive iodine at its air filter station in Svanhovd, which is by the Russian border.

The samples were collected in the period Aug. 9 through 12, while the accident in the Arkhangelsk region of northern Russia occurred on Aug. 8, it said. But it added that the anomalous measurements had no clear ties to the Russian incident.

“At present it is not possible to determine if the last iodine detection is linked to the accident in Arkhangelsk last week. DSA continues more frequent sampling and analysis,” DSA said.

Indeed, such measurements are not uncommon in Norway, as and its monitoring stations detect radioactive iodine several times a year and the source is usually unknown.

Andrei Zolotkov, who heads Bellona’s offices in Murmansk, says the iodine measurements are not cause for alarm.

“Information about the discovery of insignificant quantities of radioactive iodine periodically appear on the website of DSA, and the media always writes about them,” he said. “But these concentrations are so small that there is no sense in being alarmed by them.”

Rather than coming from the site of last week’s secrecy-cloaked accident in Akhangelsk, Zolotkov said insignificant amounts of iodine can be discharged by nuclear power stations – such as the Kola nuclear plant, which is located just across Norway’s border with Russia.

Had radioactive iodine migrated from the Archangelsk region, Zolotkov added, it would have triggered radiation detection systems in the Murmansk region before reaching Norway.