Toyota lost over $15 billion in market value last week after being caught falsifying tests

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.

The stock 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, dropped 7.7% in the same period, and lost 80.33 billion yen in market capitalization last week.

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

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

Shares of all those companies were trading higher 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