At least six construction projects at U.S. military bases in Japan were awarded in fiscal 2004 to contractors that have been searched by prosecutors investigating alleged bid-rigging at the Defense Facilities Administration Agency, investigative sources and documents indicated Monday.

The winning bids for the six contracts averaged 97.4 percent of the maximum allowable contract prices, a figure that points to the bids being rigged, the sources said.

According to investigators and records from the Hiroshima and Fukuoka bureaus of the Defense Facilities Administration, Taisei Corp., Tekken Corp., Obayashi Corp., Kajima Corp., Maeda Corp. and Penta-Ocean Construction Co. were among the construction companies that won contracts for the six projects.

More than a dozen firms have been searched by prosecutors recently in connection with bid-rigging allegations involving the Defense Facilities Administration Agency.

Five projects were linked to the relocation of a runway at the U.S. Marine Corps Iwakuni Air Station in Yamaguchi Prefecture. One was for construction of a loading dock at the U.S. naval base in Sasebo, Nagasaki Prefecture.

The agency, which manages facilities for the Self-Defense Forces and the U.S. military in Japan, put the projects out to tender.

The maximum bids for the six projects was set between 77.4 million yen and 4.06 billion yen, and the winning bids ranged between 75.6 million yen and 4.03 billion yen, the sources and documents indicated.

The highest winning bid was for the Sasebo dock construction project, in which a consortium of five construction firms, including Penta-Ocean Construction, submitted a bid of 4.03 yen, billion, 99.2 percent of the agency-set maximum of 4.06 billion yen.

The allegations are among the suspected bid-rigging cases involving current and retired senior officials at the agency.

The agency's third-ranking official, along with two others, has been arrested on suspicion of rigging bids for two Defense Agency facilities.