Suzuki admitted improper inspections on 6,401 vehicles, or nearly half of those subject to sample checking, between 2012 and 2018. Mazda said it 72 vehicles or 3.8% of those in its sample were affected, while Yamaha put the figure at 2.1% of its motorbike sample. "This is extremely regrettable as this may cause doubts among automobile users about vehicle performance and the quality-control structures of automakers," Transport Minister Keiichi Ishii said in a statement. The ministry said it would "examine their reports and take strict measures if necessary". It said most of the 20 other companies asked to examine their data had reported no misconduct, while several others were still investigating. Investors dumped shares of the three firms after the news. Suzuki tumbled 6.04% to 6,944 yen, Mazda sank 1.30% to 1,327 yen and Yamaha Motor dived 4.63% to 2,820 yen. The admissions are the latest in a string of scandals involving data falsification and testing standard breaches in Japan's key auto sector.