WASHINGTON/NEW YORK (Reuters) - The U.S. Secret Service visited the office of a Pennsylvania-based refrigeration contractor, Fazio Mechanical Services, in connection with an investigation of the Target Corp consumer data breach, a spokesman for the agency said on Wednesday. Fazio is the largest refrigeration contractor in the Western Pennsylvania region, and Target is one of its clients, according to the Sharpsburg-based company's website. A law enforcement source told Reuters that evidence suggests the hackers stole login credentials from Fazio and may have used the credentials to break into Target's network. The source added, however, that investigators were not sure that...