The Fair Trade Commission has searched the offices of four companies on suspicion they formed a cartel to control prices for fumigating plants imported through Narita airport, sources close to the case said Saturday.

The FTC searched Japan Airlines Co.'s cargo branch in Narita, Chiba Prefecture, Kokusai Kuko Uwaya, a Narita warehouse firm, and Yokohama-based sterilization firms Kanto Kogyo and Kanto Kunjo.

The four companies allegedly fixed prices to fumigate imported plants at the airport and had the two sterilization firms share orders, they said.

The 15-nation European Union demanded last October that the Japanese government deregulate fumigation work at the airport, saying costs are higher than at other airports due to a lack of competition.

According to the sources, cargo arriving at the airport is handled either by JAL's airport branch or Kokusai Kuko Uwaya, with JAL accounting for some 60 percent of the total.

Plants and grains are subject to inspection by the Ministry of Agriculture, Forestry and Fisheries. Plants that fail to pass the inspection are taken to a fumigation facility for sterilization, but this work has allegedly been monopolized by Kanto Kogyo and Kanto Kunjo, the sources said.

The two sterilization firms allegedly shared orders by taking turns to receive business from the warehouses run by JAL and Kokusai Kuko Uwaya, they said. They charge about 30,000 yen to fumigate 500 kg of plants, each making a profit of around 10 million yen a month, the sources said.

Plant imports at Narita airport were worth about 17 billion yen in 2000, of which between 20 percent and 30 percent needed fumigation, according to customs officials.

JAL and the warehouse firm are also believed to have agreed to requests from the two sterilization firms to raise charges for nighttime fumigation via consultations at a committee running the fumigation facility, the sources said. The committee comprises 17 firms.

A JAL spokesman said the FTC has ordered the airline to produce all fumigation-related documents. JAL will cooperate in the FTC investigation, the spokesman added.

The three other companies denied any wrongdoing and said they were puzzled by the investigation.