Japan's regulatory watchdog yesterday raided the offices of about 30 construction companies in Utsunomiya, a city north of Tokyo, seeking evidence of bid-rigging for public works projects.

Utsunomiya Kensetsugyo Kyokai, the local construction industry association, and 30 member companies suspected of bid-rigging were previously penalised in 1995 by Japan's Fair Trade Commission and fined Y1.5bn in surcharges.