An internal review of emissions and fuel economy tests at Nissan’s production plants in Japan showed that company inspectors used “altered measurement values” on emissions inspection reports, the company said in a statement Monday. The tests also “deviated from the prescribed testing environment,” it said.

The review found that all models except the Nissan GT-R, a two-door sports car, complied with Japanese safety standards, although Nissan did not disclose further information about that model. The company said the falsification problems ultimately did not affect fuel-economy findings.

Nissan said that it had already started investigating the falsifications and that it had retained a Japanese law firm, Nishimura & Asahi, to lead the effort.

“Nissan understands and regrets the concern and inconvenience caused to stakeholders,” the company said in a statement.

A phone number provided by the company went unanswered, and company officials did not immediately respond to an email requesting additional information.

The disclosure is the latest blow for Nissan, one of Japan’s three biggest automakers and a symbol of the country’s ability to turn out quality products at mass-market prices. In October, the automaker brought its Japanese factories to a halt and began recalling 1.2 million vehicles after it discovered that vehicle inspections had been carried out by uncertified technicians.

Mitsubishi Motors and Suzuki Motor said two years ago that they had used improper methods on tests that exaggerated the fuel economy of their vehicles. Like Nissan, Subaru said in October that its employees had improperly conducted vehicle inspections.

More broadly, a number of Japanese factory owners have been rocked in recent years by safety and quality issues. The air bag-maker Takata has been blamed for a dozen passenger deaths, leading to the largest auto recall in history. Last year, it filed for bankruptcy protection in the United States and Japan.

Kobe Steel, a major Japanese manufacturer, said in November that its employees had falsified quality data for years and other companies scrambled to assess the possibility of their own inspection problems.

Unlike Takata, the other scandals have not been blamed for any deaths or injuries.

Nissan shares fell nearly 5 percent Monday after the company told investors it would be making an announcement about quality issues that afternoon. Shares of its sister company, Renault of France, were down 1 percent as of midday.

This article originally appeared in The New York Times.

Carlos Tejada © 2018 The New York Times