Prosecutors continued nationwide raids on offices of three leading water pipe manufacturers Tuesday, following the arrests of 10 officials of the firms Monday in connection with a probe of an illegal market-share cartel.

The suspected cartel involving Kubota Corp. and Kurimoto Ltd., both based in Osaka, and Nippon Chutetsukan K.K., based in Tokyo, would be a violation of the Antimonopoly Law.

Arrested at Kubota were Kotaro Tasaka, 57, head of the first sales division of the firm's Tokyo office; Takami Kusuno, 57; and Yuki Kobayashi, 52, who ran the steel pipe business at the Tokyo headquarters.

The Nippon Chutetsukan officials arrested were Hiroyuki Yamaguchi, 59, Taichi Kimura, 60, and Katsuji Shiraishi, 50. Yamaguchi is the executive managing director. The officials arrested at Kurimoto were Hiroshi Kano, 58, Kaoru Kondo, 54, Mitsuhiro Kuriyama, 57, and Masao Tomo, 53.

The Tuesday morning raids were conducted at offices in Sapporo, Sendai, Nagoya and Fukuoka, on the heels of raids Monday and Friday of Nippon Chutetsukan offices and the headquarters of Kubota Corp. and Kurimoto in Osaka and Tokyo. Documents have been seized as evidence of the companies' alleged antitrust violations.