Mazda has been implicated for the first time in a series of emissions testing scandals at Japanese automakers, while Suzuki was one of the first companies found to have falsified data, a Japanese newspaper reported.

Suzuki Motor, Mazda Motor and Yamaha Motor conducted improper fuel economy and emissions tests on their vehicles in Japan, the Nikkei said.

It was the latest in a growing list of compliance scandals in the country's vehicle industry and was confirmed by the inistry of Land, Infrastructure and Transport, the paper said.

The three companies submitted reports on the findings to the ministry in response to a request for all domestic automakers to investigate compliance procedures after Nissan Motor and Subaru were found to have falsified testing data earlier this year.

The suspect tests were performed on samples of manufactured vehicles selected during the quality assurance process. Samples were found to have been tested under incorrect driving conditions.

According to the Nikkei, Suzuki unearthed improper tests on 6,401 units out of 12,819 since 2012. Mazda detected inappropriate testing on 72 vehicles out of 1,875 since 2014, while Yamaha found seven instances out of 335 since 2016.

Suzuki President Toshihiro Suzuki apologised for his company's actions at a news conference on Thursday afternoon (9 August).

"It is a significant fact that such a large number of our products were improperly processed, and we take it seriously," he said. "We failed to educate our staff in an in-depth and extensive manner."

The automaker is not considering product recall at this moment, he added.

This is the first time Mazda has been implicated in a quality compliance scandal since the first in a series of such cases emerged at Mitsubishi Motors and Suzuki in 2016, the Nikkei noted.

Mazda said in a statement sent to just-auto the investigation covered JC08 and WLTC testing modes and key findings were no improper alteration or falsification of test data in either mode but test data containing speed trace errors was found in 72 cases out of 1,472 vehicles tested under the JC08 mode.

It said: "The company has identified two reasons for these errors. Firstly, the system was not set up to automatically invalidate results when a speed trace error occurred. Secondly, test procedures left the determination of speed trace errors up to each individual inspector.

"All test data has been re-examined and the results show there was no effect on specification fuel economy and emission figures. No such cases were found in WLTC mode testing."

Mazda will update its system to automatically treat test results as invalid in the event of a speed trace error and it has increased the number of employees who check inspection data, including speed trace errors.

"Mazda accepts that errors were made on a small number of tests and the situation was identified quickly and steps have been put in place to avoid it happening in the future," the automaker said.

The Nikkei said the transport ministry would change its ministerial ordinance to request automakers save test results of manufactured vehicles and take measures to prevent alteration of results.

"It is extremely regrettable that this situation makes users anxious over the quality of vehicles and the quality control operations of carmakers," said transport minister Keiichi Ishii.

Masataka Kunugimoto, managing director at Nomura Securities, told the Nikkei the impact on business performance would be "very minor if any". 

"It seems that foreign customers do not mind these incidents as they do not really affect the performance of the car itself," he said, citing similar previous cases.

Subaru submitted a report in April that it said detailed the extent of its falsifying of fuel economy and emissions data, as well as testing cars under conditions not recommended by the government. But the company was forced to admit in June that the problem affected roughly double the number of sample vehicles.

Nissan owned up to its own fuel and emission cheating last month. Additionally, both Subaru and Nissan used unqualified inspectors to perform final vehicle checks.

The Nikkei said there was no indication Toyota, Honda or Daihatsu had carried out improper final vehicle inspections. However, the new revelations mean that four of the eight passenger car makers in Japan have been exposed for the practice.

When the first of the scandals surfaced in 2016, Mitsubishi Motors and Suzuki Motor were found to have conducted fuel economy tests during the vehicle development phase in a manner that did not comply with domestic regulations.  

Improper final vehicle inspections, such as those uncovered this week, are "not something intended to deceive the consumer", Takaki Nakanishi, CEO of the Nakanishi Research Institute, told the Nikkei.

In the eyes of consumers, however, the reputation of Japan's auto industry has been undermined.

Experts say that it is imperative for automakers to ensure compliance with industry regulations and put in place systems to prevent recurrence if they are to repair the damage to their brands.