University of Tokyo Hospital, a top-grade medical institution under the country's most prestigious university, became the scene of a police search Wednesday following the arrest of four people, including a hospital official, in connection with bid-rigging over a maintenance project.

Kazusuke Matsumoto, 30, of the administrative division, was arrested Tuesday along with three other people, the Metropolitan Police Department said, adding the four have admitted involvement in the bid-rigging.

Police identified the three others as Atsuto Matsuda, 27, of Nippon Kanzai Co., Koji Ishikawa, 38, of SNK Service Co., and Kimio Tachihara, 59, formerly of SNK.