Honda became the fourth Japanese carmaker to be inspected by the transport ministry for improper vehicle certification tests, following Toyota, Yamaha, and Suzuki. Over 30 models from Honda, Toyota, Yamaha, and Suzuki were found not to have undergone proper certification for safety and environmental performance. The transport ministry has ordered a halt to shipments of six models still in production. Discrepancies in certification testing were also found last year at Daihatsu and Toyota Industries, prompting investigations.