Mazda, Suzuki and Yamaha Motor had followed the admissions of Japanese manufacturers Nissan and Subaru in admitting to improper testing of vehicles for fuel economy and emissions.

Japan’s transport ministry ordered automakers to review their testing procedures and carry out internal investigations into their vehicle testing practices after Nissan and Subaru admitted that they had falsified final inspection results on cars destined for their home market.

Suzuki admitted at a press conference today (August 9) that half of the 12,819 sample cars tested for fuel economy and emissions were inspected under invalid conditions.

Around 4% of the cars inspected by Mazda – just over 70 cars – displayed evidence of irregularities, meanwhile, with 2% of motorbikes raising concerns in Yamaha’s case.

Reuters reported that the Transport Ministry had stated that Suzuki, Mazda and Yamaha had cleared vehicles for emissions or fuel efficiency even in cases where they were tested under invalid conditions.

All three brands issued public apologies today.

Speaking at a press conference in Tokyo, Suzuki chief executive Toshihiro Suzuki said of the brand’s testing procedure: “The checking mechanism was insufficient. We regret that we left the inspections to factories.”

Last month Nissan Nissan admitted that emissions and fuel economy data had been deliberately falsified at most of its factories in Japan.

The Japanese car manufacturer admitted the “misconduct” as it reported the results of its investigation into “nonconformities in the final vehicle inspection process” to the Japanese Ministry of Land, Infrastructure, Transport and Tourism.