Police on Jan. 27 arrested five officials belonging to a mutual aid society affiliated with Upper House member Tatsuo Tomobe, 68, on suspicion of massive fraud.The five arrested include Tomobe's wife, Mikiko, 61, who is the head Orange Kyosai Kumiai, and his son, Momoo, its 29-year-old managing director, the sources said. Police are expected to request the lifting of Tomobe's immunity to arrest from Diet so he can be taken into custody as well.The Metropolitan Police Department and other prefectural police made the arrests of the five directors of Orange Kyosai Kumiai, which is run by a political support group for the Upper House legislator, the sources said. Matsunosuke Ishizaki, a former director of the society, was also arrested. Police questioned Tomobe on Jan. 27 at a Tokyo hospital, where he has been admitted as a stroke patient.The Constitution stipulates that Diet members cannot be arrested during a legislative session unless the lawmakers are caught in the act of committing a crime or unless given permission by the legislature. The Diet is presently in a 150-day ordinary session. Upper House sources said if police would seek the lifting of Tomobe's immunity from arrest, the chamber would deal with the matter in accordance with due processes and probably comply with the request, if made.Thirteen Diet members, including former Lower House member Toshio Yamaguchi, have been placed under arrest while still in office since the end of World War II after the legislature stripped them of their immunity from arrest as requested by police. Two were Upper House members.