The "Yomiuri" was the center of a labor scandal in 1945 and 1946. In October, 1945, a postwar "democratization group" called for the removal of Shoriki Matsutaro, who had supported Imperial Japan's policies during World War II. When Shoriki responded by firing five of the leading figures of this group, the writers and editors performed the first "production control" strike on 27 October 1945. This method of striking became an important union tactic in the coal, railroad, and other industries during the postwar period. Shoriki Matsutaro was arrested in December 1945 as a Class-A war criminal and sent to Sugamo Prison. The "Yomiuri" employees continued to produce the paper without heeding executive orders until a police raid on June 21, 1946. Matsutaro was released in 1948 after agreeing to work with CIA as a collaborator and informant, according to research by Professor Tetsuo Arima of Waseda University, based on declassified documents stored at NARA.