TOKYO -- Mazda and Suzuki improperly tested vehicles for fuel economy and emissions, the Japanese government said on Thursday, in the latest cases of data falsifications by the nation's manufacturers.
The government had ordered the automakers to make checks after revelations of improper testing at Subaru and Nissan last year.
Suzuki and Mazda cleared vehicles for emissions or fuel efficiency even in cases where they were tested under invalid conditions, the ministry said in a statement. The ministry looked at tests done for different periods at the two automakers, and at motorcycle maker Yamaha, stretching back to 2012 in Suzuki's case.
Suzuki, Japan's fourth-largest automaker, said that of 12,819 sample cars tested for fuel economy and emissions since June 2012, around 50 percent had been inspected improperly.
"I deeply apologize and will lead efforts to prevent recurrence," CEO Toshihiro Suzuki told a news conference.
Suzuki said it did not find any significant problems with actual emissions and fuel economy performance and therefore planned no recalls.
The ministry said it found irregularities in 4 percent of similar inspections on Mazda cars. It also found irregularities in 2 percent of inspections on Yamaha motorbikes.
Yamaha also confirmed it carried out inappropriate testing, and apologized. Mazda said it would hold a news conference later in the day.
In July this year, Nissan Motor Co. admitted it had improperly measured exhaust emissions and fuel economy for 19 vehicle models sold in Japan.
The growing list of improprieties has tarnished the image of the country's manufacturing industry, known for high-quality, efficient production.
Kobe Steel, Mitsubishi Materials Corp. and Toray Industries -- all key suppliers of motor parts to global manufacturers -- admitted to product data fabrication last year.
Japanese automakers, already hit by lackluster sales, have also been under pressure from U.S. President Donald Trump's proposed tariffs on imported vehicles.