A mysterious halt in Iran's uranium enrichment activities earlier in November, as revealed in a new report by the UN atomic watchdog, may have been due to a cyber attack, experts suggested on Thursday.
But the enrichment programme is vulnerable to wider technical problems - particularly since it uses outdated technology - as well as international sanctions, the experts argued.
A restricted report by the International Atomic Energy Agency, a copy of which was obtained, says no uranium-enriching centrifuges at Iran's enrichment facility in Natanz were being fed with nuclear material on at least one day in November.
Centrifuges are finely calibrated cylindrical devices that spin at supersonic speed to separate out an isotope of uranium used to make nuclear fuel or, if refined to a much higher degree, for the fissile material for an atomic bomb.
"On November 16, no cascades were being fed with UF6" or uranium hexafluoride, the nine-page report revealed, without offering any explanation as to a possible cause of the outage.
Uranium hexafluoride, a toxic gas, is the particular form of uranium used in the enrichment process.
Most of the machines at Natanz are used to produce low-enriched uranium or LEU, which is used to make nuclear fuel.
A much smaller pilot plant where earlier this year Iran began enriching uranium to 20 percent purity - ostensibly to produce radioisotopes for medical purposes - was not affected.
The IAEA's inspectors were not yet able to determine exactly how long the halt lasted: a few hours on November 16, an entire day or even longer.
The inspectors have not been back since, but Iranian authorities informed them that on November 22 nuclear material was being fed back into the centrifuges.
Iran quickly ruled out a possible cyber attack and denied that the enrichment work was experiencing technical problems.
But experts see as "feasible" the theory that the stoppage was caused by a computer worm called Stuxnet that has infiltrated Iran's nuclear facilities recently.
Israel is suspected of designing Stuxnet to sabotage its arch foe's nuclear programme, which the West believes is simply a cover to build an atomic bomb, though Iran denies it.
"It's certainly feasible, because of the kind of technical problems it can cause in the control systems for centrifuges," said Mark Hibbs, senior associate at the Carnegie Endowment for International Peace.