OSAKA -- Police searched on Sunday the headquarters of Hanshin Expressway Public Corp. for evidence to support allegations that the company illegally favored a particular bidder for road-related work.

On Saturday, a former deputy manager of the public road entity's Osaka administration department and three others were arrested in connection with the alleged crime.

Yorimichi Maekawa, 59, the former manager, is suspected of having committed the offense in December 1999.

The three others are Yasuo Kondo, 55, who currently holds Maekawa's position at the corporation; Masao Yamamoto, 62, chairman of Kokuyo Kensetsu; and Akira Tanimoto, 56, a business department manager of Kokuyo's affiliate Kyodai Kensetsu.

According to police investigations, Maekawa and Kondo chose nine firms in business fields similar to that of Kyodai Kensetsu, but who were uninterested in the bidding, to replace soundproof walls on the expressway's Higashi-Osaka Line. The work took place Dec. 27, 1999.

Maekawa and the others allegedly arranged the bid rigging and told Kyodai Kensetsu the expected contract price. The firm ended up winning the bid for 171 million yen, about 98 percent of the price.

Police suspect that such works have regularly been monopolized by more than 10 Kokuyo-related firms through similar methods, that willing companies have been unfairly treated and that other top officials of the public corporation were also involved in similar bid-rigging cases.

Several firms that took part in the bid in question told police they never seriously believed they would win the contract. They said they knew the winner had already been chosen, the sources said.

It was also discovered that most of the firms that secured the contracts had been hiring retired Hanshin Expressway officials. Investigators believe the suspects selected such firms because they would be more willing to comply with their plans.