Major construction company Shimizu Corp., already linked to bid rigging involving the Defense Facilities Administration Agency, won contracts worth nearly 9 billion yen from the agency without undergoing public tenders, documents show.

An agency official confirmed the deals but defended them, saying the agency gave the contracts to Shimizu or Shimizu-led joint ventures in consideration of the confidentiality of the work and the contractor's expertise.

A law regulating single tendering by the public sector allows exceptions when the worth of the project is less than 2.5 million yen or when the nature of the work dictates this approach.