A Hungarian manufacturer of medical radioactive substances was "most probably" the source of increased radiation levels measured in several European countries in the past weeks, the U.N. nuclear agency said Thursday.
The Vienna-based International Atomic Energy Agency said in a statement that it had received the information from Hungarian nuclear authorities, adding the measured levels of iodine-131 were "extremely low."
"There is no health concern to the population," the IAEA said.
Jozsef Kornyei, director of the Budapest-based Institute of Isotopes Co., said that the firm first noticed the heightened release of iodine-131, used in the treatment of thyroid disorders, during the first half of 2011.
Production restarted in September after new filters were installed, but the release of radioactive material stayed above normal levels, so the process was halted again this month.
Kornyei told the AP in a phone interview that new ventilators were being added at the plant in an effort to limit the excessive release of the radioactive material and that production of iodine-131 would not be restarted until next year.
Citing weather factors and the very low radioactivity of the iodine-131 released into the atmosphere, Kornyei said it was "extremely unlikely" that the leak at the Budapest plant was the cause of trace levels of iodine-131 measured in several European countries.
The IAEA was initially notified about the higher iodine-131 levels by the Czech Republic on Nov. 11. Similar reports came later from Austria, Slovakia, Germany, Sweden, France and Poland.
A letter sent Thursday to the IAEA by the Hungarian Atomic Energy Authority said the cause of the higher radioactivity was under investigation, albeit hampered by administrative difficulties.
"Unfortunately, in Hungary the licensing and surveillance of the nuclear facilities and the laboratories using high amounts of radioisotopes are in the hands of different authorities," the Hungarian nuclear watchdog said.
"The communication problems we faced in the present situation call our government's attention for an improvement and simplification of our regulatory system," it said.
Correspondent George Jahn in Vienna contributed to this report.