The Committee investigated the five largest detective agencies: the Pinkerton National Detective Agency, the William J. Burns International Detective Agency, the National Corporation Service, the Railway Audit and Inspection Company, and the Corporations Auxiliary Company. Most of the agencies subpoenaed, including the Pinkerton Agency, attempted to destroy their records before receiving the subpoenas, but enough evidence remained to "piece together a picture of intrigue". It was revealed that Pinkerton had operatives "in practically every union in the country". Of 1,228 operatives, there were five in the United Mine Workers, nine in the United Rubber Workers, seventeen in the United Textile Workers, and fifty-five in the United Auto Workers that had organized General Motors.