Police said on Thursday (November 29) they had seized 481.4 grams (17 ounces) of enriched uranium and arrested two Hungarians and one Ukrainian on Wednesday (November 28) in a raid along the border with Hungary, near to the frontier with Ukraine. Enrichment raises the proportion of the 235-type uranium in the material, which can yield fuel for nuclear power stations or be used to make nuclear warheads. Police did not say to what level the uranium was enriched, but said the material, found in two cases, contained two types of uranium known as 235 and 238 isotopes. Slovak police Vice-President Michal Kopcik (pron: Kop-tsheek) told reporters about the operation. "Yesterday around 2 p.m. policemen from the 'Department for Fight against Organised Crime' together with their Hungarian colleagues caught three people who had tried to sell radioactive material. One is Ukrainian, another is Hungarian but has lived in Ukraine for a long time and the third is Hungarian. These three people were offering 481,4 grams of radioactive material Uranium 235 and 238," said Kopcik. "This material could possibly be used for production of a so called "dirty bomb" and it could be also used for the purposes of terrorism," Kopcik told a news conference. A dirty bomb is an explosive device that spreads radioactivity but the blast itself is caused by non-nuclear material. Police said the suspects were detained on their way to a meeting where they wanted to sell the material for 3,500 U.S. dollars per gram, making the total amount seized worth nearly 1.7 million U.S. dollars, and had entered Slovakia from Hungary. Police had originally reported the amount seized was 1 kg, but officials said on Thursday that was original information that had been provided by the three suspects. Police said the material probably came from the former Soviet Union, but did not specify which country. Independent British nuclear consultant John Large said Ukraine had been the Soviet Union's main uranium processing centre and still houses a vast amount of uranium waste. Police in Slovakia's former federation partner, the Czech Republic, found 2.73 kg of high-enriched uranium in the capital Prague in 1994, intended for illegal sale. It was the second biggest seizure of high-enriched uranium after a 1994 find of 2.97 kg in the Russian city of St. Petersburg, according to the International Atomic Energy Agency.