Nov. 11, 2011  -- The hunt is on for the source of low level radiation detected in the atmosphere "across Europe" over the past weeks, nuclear officials said today.

Trace amounts of iodine-131, a type of radiation created during the operation of nuclear reactors or in the detonation of a nuclear weapon, were detected as early as three weeks ago by Austrian authorities and then two weeks ago by the Czech Republic's State Office for Nuclear Safety. Today the International Atomic Energy Agency released a statement revealing similar detections had been made "in other locations across Europe."

The IAEA said the current levels of iodine-131 are far too low to warrant a public health risk, but the agency still does not know the origin of the apparent leak and an official with the agency would not say where else it has been detected. Considering iodine-131 has a radioactive decay half-life of about eight days, continued detection means the leak occurred over a period of several days at least and is possibly ongoing.

The IAEA said it does not believe the radiation was left over from the nuclear disaster at Japan's Fukushima Daiichi plant in March and the Czech Republic's State Office for Nuclear Safety said it was unlikely to have been caused by an incident at any nuclear plant's core. A meltdown there, the Czech agency said, would have released several other radioactive isotopes in addition to iodine-131.

The IAEA has been unable to determine from which country the radiation is emanating, and both Czech and Austrian officials said it was unlikely their countries were the source. Austrian officials said in a statement that a study of the dispersal cloud indicated the radiation is most likely coming from somewhere in southeastern Europe.

In addition to nuclear plants, iodine-131 is used in many hospitals and by radiopharmacutical manufacturers as it can be used to help treat thyroid problems in small doses.

"Anywhere spent nuclear fuel is handled, there is a chance that... iodine-131 will escape into the environment," the U.S. Environmental Protection Agency says on its website.