Rumors had circulated about Hiss since 1939, when Chambers, at the urging of anti-Stalinist Isaac Don Levine, had gone to Assistant Secretary of State Adolf A. Berle, Jr. and accused Hiss of having belonged to an underground communist cell at the Department of Agriculture. In 1942, Chambers repeated this allegation to the FBI. In 1945 two other sources appeared to implicate Hiss. In September 1945, Igor Gouzenko, a 26-year-old Ukrainian whose three-year tour as a cipher clerk stationed at the Soviet Embassy in Ottawa was coming to an end, defected from the Soviet Union and remained in Canada. In exchange for asylum, Gouzenko offered to Canadian authorities evidence about a Soviet espionage network actively working to acquire information about nuclear weapons, along with information that an unnamed assistant (or more precisely an "assistant to an assistant") to U.S. Secretary of State Stettinius was a Soviet agent. When informed of this, Hoover assumed Gouzenko was referring to Alger Hiss. Three months later (in December 1945), Elizabeth Bentley, an American spy for the Soviet Union, who served also as a courier between communist groups, told the FBI, as documented in the FBI Silvermaster File that "At this time Kramer told me that the person who had originally taken Glasser away from Perlo's group was named Hiss and that he was in the U.S. State Department." Bentley also said that the man in question, whom she called "Eugene Hiss" worked in the State Department and was an adviser to Dean Acheson. In both cases (Gouzenko and Bentley), the FBI decided that Alger Hiss was the likely match. Hoover put a wiretap on Hiss's home phone and had him and his wife investigated and tailed for the next two years.