The scandal took a $15.6 billion bite out of the company’s market cap as its shares fell by more than 5.4% last week, CNBC reported. Toyota’s Nasdaq-listed shares were up about 1% as of Monday afternoon. 

Through an internal investigation prompted by a regulator mandate, Toyota found it had not performed safety tests as certification required in five cases related to vehicles including the Crown, Corolla, and the Yaris Cross. In one case involving the Lexus RX, the company had submitted falsified data to meet safety standards and submitted it for certification.

Although the company maintained the vehicles affected by the scandal were safe to drive, Toyota’s chairman Akio Toyoda apologized in a press conference last week.

“As the person responsible for the Toyota Group, I would like to extend my sincere apologies to our customers, car enthusiasts, and all stakeholders for this issue,” he said. 

Toyota said it would suspend production of three models—the Corolla Fielder, Corolla Axio, and Yaris Cross—based on the findings from its investigation. The company sold more than 11 million total vehicles worldwide last year. 

Toyota rivals Honda, Mazda, and Suzuki also admitted to falsifying data related to safety certification tests in what amounted to a week of setbacks for Japanese automakers. Mazda, which is Japan’s second-largest automaker, suspended production of the Roadster RF and Mazda 2, while company shares sank more than 7% last week, resulting in a $500 million hit to its market cap, CNBC reported.

The safety scandal involving several Japanese automakers risks damaging the stellar reputation that companies such as Toyota and Nissan have cultivated, especially in North America, the companies’ biggest market. 

Japan’s transport ministry earlier this year ordered 90 car manufacturers to reexamine how they test their vehicles after a Toyota affiliate was found to have falsified data related to safety for decades.