American investigators are also verifying a report by a taxi driver, who said that on the night of one of the break-ins he had driven Hebrew-speaking passengers who asked to be let off at Greenberg's office.

Last week, FBI agents collected evidence, including blood, from the Greenberg's office. Police and FBI agents have questioned former employees of the firm during their investigation of the burglaries, in which campaign files related to Barak's campaign were stolen.