Responding to a parliamentary question, health minister Lydia Mutsch said that a Luxembourg station had sporadically detected traces of Iodine-131 since the start of 2017.

She said: “The quantities measured were extremely low, close to the threshold for detection.”

Iodine-131 is a radioisotope of iodine, which is present in nuclear fission products and in high doses can cause mutation and death in cells that it penetrates.

Increased radiation at trace levels were detected across Europe in January 2017.

The levels were thought to have been linked to a radioactive leak at a nuclear reactor in Norway in October 2016.

The leak was caused by a technical failure during treatment of the fuel in the reactor hall.

It was contained and, according to the Norwegian authorities, no radioactive contamination was detected outside the facility, the minister said. 

She added that the amount of reactive iodine leaked was equivalent to 10% of the permitted limit.

Meanwhile, the source of the traces of radioactive Iodine-131 remains unknown.