The Fair Trade Commission searched about 10 major contractors Tuesday for evidence that they rigged bids to get construction contracts from the Defense Facilities Administration Agency, sources said.
The general contractors include Taisei Corp., Shimizu Corp. and Obayashi Corp.
The antimonopoly watchdog alleges the companies rigged bids for contracts awarded between January 2004 and March 2005.
The contracts include those for relocating a runway at the U.S. Marine Corps Air Station Iwakuni in Yamaguchi Prefecture, and for building a pier at a U.S. Naval base in Sasebo, Nagasaki Prefecture.
Tokyo prosecutors indicted three former senior officials of the agency earlier this year in connection with the scam and fines have already been imposed on eight executives of the contractors implicated.
The Land, Infrastructure and Transport Ministry ordered the eight firms to suspend business for 30 to 60 days starting May 26.