STORY: Japanese transport ministry officials arrived at Toyota's headquarters on Tuesday (June 4) to begin an onsite probe over a widening vehicle certification scandal.

The fallout involves five domestic automakers, who were found to have submitted either flawed or manipulated data when applying to certify some vehicle models.

Authorities said on Monday they would also be inspecting Mazda, Honda, Suzuki and Yamaha Motor.

The issue emerged after the ministry requested automakers in late January to investigate certification applications, following a safety test scandal at Toyota's Daihatsu compact car unit that emerged last year.

Toyota's chairman apologized for the company's wrongdoings on Monday (June 3), admitting that some cars did not go through the correct certification process before being sold.

Toyota, the world's largest automaker by volume, has now suspended sales of some models, as has Mazda.

Though both said there were no performance issues that violated regulations, and told customers they did not need to stop using their cars.