Tokyo (From news reports) -- Japan's Fair Trade Commission on Tuesday conducted on-site inspections of seven facilities linked to paper distributor Japan Pulp and Paper Co. and three other companies over suspected bid-rigging.

The four companies underwent the inspections for alleged antimonopoly law violations, as they are suspected of rigging bids for contracts with the National Printing Bureau for the supply of paper for the government's official gazettes.

According to informed sources, the three others are Kokusai Pulp & Paper Co., which is a subsidiary of KPP Group Holdings Co., NP Trading Co., which is a unit of Nippon Paper Industries Co., and Fukui Shigyo.

The four are suspected of prearranging winners of the biddings to keep contract prices at high levels. The suspected malpractice is believed to have started around 10 years or more ago, according to the sources.

Orders placed for paper for the government's official gazettes annually reach around 150 million yen.