Shares of Japanese automakers have largely plunged since the country’s transport ministry found false data used to certify certain models a week ago on Monday.

Shares of Japan’s largest carmaker Toyota fell more than 5.4% last week, after the scandal broke on June 3, but is recovering on Monday. The automaker lost 2.45 trillion Japanese yen ($15.62 billion) in market value last week alone.

Shares of Mazda, the country’s second largest automaker, fell 7.7% in the same period, and lost 80.33 billion yen, or $511.8 million in market capitalization last week.

The wide ranging inspection by the Ministry of Land, Infrastructure, Transport and Tourism ministry also found irregularities in certification applications by other automakers Honda, Suzuki and Yamaha.

Last week, Honda’s stock fell 5.75%, Yamaha Motor lost 2.2%, while Suzuki Motor inched down 0.3%.

Shares of all those companies were trading higher on Monday. Toyota was up 1.7%, Honda gained 2.13% and Mazda increased 1.7%. Suzuki and Yamaha were also marginally higher.

All five companies had submitted false test data, or in the case of Toyota and Mazda, falsified the vehicles used in crash tests.

Toyota announced on June 3, following the ministry’s investigation report, that it will temporarily halt shipments and sales of three models currently manufactured in Japan, namely the Corolla Fielder, Corolla Axio, and Yaris Cross.

Toyota’s Chairman Akio Toyoda apologized to the company’s customers and stakeholders, acknowledging that seven of its models were “tested using methods that differ from the standards defined by the national authorities.”

Separately, Mazda said it had suspended the Roadster RF and Mazda 2 from May 30.

Both companies however, said that customers can still continue to drive their cars.

The transport ministry said it will conduct on-site inspections of the five companies where misconduct was reported.

The inspection into Japanese automakers comes after Toyota’s Daihatsu unit said in December it will halt shipments of all vehicles both overseas and in Japan. It came after an investigation into a safety scandal found issues at some 64 models, including 22 sold under the Toyota brand.

Daihatsu said in April last year it had rigged side-collision safety tests carried out for 88,000 small cars, most of which were sold under the Toyota brand.