Suspect material recently seized by Kyrgyz police turned out to contain only harmless amounts of plutonium, a UN official has told BBC News Online.
Initial reports spoke of two men being arrested on suspicion of trying to sell "plutonium containers" near the ex-Soviet republic's capital, Bishkek.
But a spokesperson for the UN's nuclear watchdog said the containers were 55 old-fashioned Soviet smoke detectors.
Such detectors contain
a few micrograms of plutonium but are quite harmless.
Melissa Fleming, a spokesperson for the International Atomic Energy Agency (IAEA) in Vienna, told the BBC on Thursday that Kyrgyz officials had confirmed the containers were stolen smoke detectors of a type produced 20 to 30 years ago in the USSR.
The containers did not, she said, pose a threat "from the point of view of nuclear proliferation", and Kyrgyzstan did not appear to be any more dangerous than other countries in this respect.
However, Ms Fleming added that the fact that there were clearly people who believed they could find buyers for plutonium on the black market continued to cause concern.
The IAEA was calling for tighter controls over potential "ingredients" for illegal nuclear weapons, she said.
The World Nuclear Association notes that a type of smoke detector commonly available in many countries uses the radiation from a small amount of radioactive material to detect the presence of smoke or heat sources.
"Ion chamber" smoke detectors, as they are known, are popular because they are inexpensive and are sensitive to a wider range of fire conditions than other designs, the WNA adds.