Hungary's nuclear authority told the International Atomic Energy Agency that iodine-131 had been released from the Institute of Isotopes Ltd from September 8 to November 16.
"The cause of the release is under investigation," the Vienna-based IAEA said in a statement.
"The levels of Iodine-131 that have been detected in Europe are extremely low. There is no health concern to the population." Iodine-131, linked to cancer if found in high doses, can contaminate products such as milk and vegetables.
The IAEA, the Vienna-based U.N. nuclear watchdog, announced on Friday that the traces had been detected in Europe, after it was tipped off by authorities in the Czech Republic.
Authorities in Austria, Slovakia, Hungary, Germany, Sweden, France and Poland have measured very low levels of iodine-131 in their atmospheres over the past few days.
The Hungarian institute, which produces radioisotopes for healthcare, research and industry, said earlier on Thursday that it had suspended production.Mihaly Lakatos, director of the institute, said that despite the higher than usual emission of the isotope, Hungary could not have been the source of the leakage registered in several European countries over recent weeks.
"The amounts of iodine-131 measured in neighboring countries cannot have much to do with this, because the distances involved rule out that the amount we emit could be registered over there," he told Reuters.
DOUBT
However, Jozsef Ronaky, director of the Hungarian Atomic Energy Authority, said it was too early to draw such a firm conclusion.
"It cannot be ruled out (that the institute was the source). I consider the opinion of the laboratory premature. Establishing whether the substance detected in other countries was emitted by them requires a thorough investigation," he told Reuters.Ronaky said the body, which has no oversight of the Institute of Isotopes but is the IAEA's point of contact in Hungary, has submitted all relevant Hungarian data to the U.N. nuclear watchdog. "I think it is probably us, that is the Institute of Isotopes, that is the source," he said.
Ronaky said he has initiated a thorough inquiry involving the institute and national authorities to explore how potential issues of technology, oversight and communication could be addressed.
The Hungarian Medical Officer Service, which is in charge of overseeing the laboratory, could not immediately comment.
The Institute of Isotopes is 69-percent owned by the Hungarian Academy of Sciences, while the rest is owned by Hungarian private investors.
Budapest's envoy to the U.N. agency also said earlier he could not rule out that the lab was the source. The IAEA said that if a person were to breathe in the levels for a whole year, they would receive an annual radiation dose of less than 0.1 microsieverts.
In comparison, average annual background radiation is 2,400 microsieverts a year, it said.