The levels of radiation measured are very low and pose no threat to humans, and so far no radiation spikes have been detected in the Island.
Increased Iodine-131 levels have been recorded in many major European cities from Norway to Spain – but scientists have yet to work out where the radiation comes from.
Conspiracy theorists are suggesting the cloud is radioactive fallout from secret Russian bomb testing or an unreported nuclear accident. None of the claims have been verified.
Caroline Maffia, assistant director of Environmental Health in Jersey, said the department was aware of the situation but 24-hour-a-day air monitors placed across the Island had not detected anything yet.
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