ST. PETERSBURG -- A butcher, a plumber and a factory worker have been arrested and accused of trying to sell $600,000 worth of stolen enriched uranium on the black market, officials said Wednesday. A fourth suspect, a worker at the secret facility from which the uranium-235 was stolen, has been apprehended near Moscow and accused of smuggling the uranium out in a rubber mitten, according to Yury Reshetnikov, a spokesman for the Interior Ministry. Reshetnikov said a team of St. Petersburg nuclear physicists aiding the investigation had determined that the uranium was meant for use as reactor fuel and was not sufficiently enriched to be used in nuclear weapons. Western governments are worried that in the chaos of post-Soviet Russia, criminals might easily get their hands on nuclear technology. The director of the U.S. Federal Bureau of Investigations told a Congressional hearing last month that he feared criminal gangs might even be able to obtain nuclear weapons and sell them to terrorists. Officials at the Vienna-based International Atomic Energy Agency reached by telephone declined to comment on the importance of the theft, saying they would have to wait for an official report from Russian authorities to form an opinion.Authorities say that an employee at a secret plant producing fuel for nuclear reactors near Elektrostal in the Moscow region, identified only as Shevelyov, has been accused of having stolen two kilograms of uranium. Vladimir Borzilov, an official at the Russian Public Prosecutor's office, said Shevelyov allegedly stole the uranium as long ago as the spring of 1992.In March 1994, authorities say, Shevelyov dispatched his son to St. Petersburg to sell the uranium there. Soon after, the Federal Counterintelligence Service arrested Shevelyov's son and his two associates in St. Petersburg and police later apprehended Shevelyov near Moscow. If convicted, the men could face sentences of up to 10 years in jail and could have all of their property confiscated by the state.Borzilov said Wednesday that investigators did not know where the four suspects had stored the radioactive material for two years.But Yevgeny Lukin, a spokesman for the Federal Counterintelligence Service, said the men took no safety precautions with their dangerous merchandise. "They kept it in an apartment, in the refrigerator, in half-liter glass jars," Lukin said. "The usual kind of jars you see everywhere, the kind that hold juice or tomato paste. Some of the uranium was also kept in a metal test tube."Reshetnikov said police had received reports that the uranium was to be sold to Sweden. Lukin said that the men were looking for a foreign buyer. He added that enriched uranium of that sort would sell for about $300 a gram, or about $600,000 total."When they would go to see prospective buyers, they would take a jar out of the fridge, pop it into a sack and go," Lukin said. "Thank God they never accidentally dropped a jar on the street."Lukin said that authorities had waited three months to report the crime because they feared frightening city dwellers into thinking their apartment buildings might be radioactive.Lukin said the alleged thieves "probably received a substantial dose of radiation," and that the apartment building where they and their families lived had become contaminated with radiation and had to be cleaned.