Toyota Motor (7203.T) and Mazda Motor (7261.T) temporarily halted shipments or sales of some vehicles after Japan's transport ministry found irregularities in applications to certify their models.
The ministry said on Monday irregularities were found in applications to certify models from the two automakers and also from Honda Motor (7267.T), Suzuki Motor (7269.T) and Yamaha Motor (7272.T). It had ordered Toyota, Mazda and Yamaha to suspend shipments of some vehicles.
The developments represent a widening of a safety test scandal among Japanese automakers. The ministry had requested automakers to investigate their vehicle certification applications following a safety test scandal at Toyota's compact car unit Daihatsu that emerged last year.
Toyota, the world's biggest automaker by volume, said on Monday it has temporarily halted shipments and sales of three car models made in Japan. Chairman Akio Toyoda will hold a press conference at 0800 GMT on Monday.
The transport ministry said separately it will conduct an on-site inspection at Toyota's headquarters on Tuesday.
Mazda suspended shipments of its Roadster RF sports car and the Mazda2 hatchback from Thursday last week after finding workers had modified engine control software test results, it said in a statement.
It also found crash tests of the Atenza and Axela models that were no longer in production had been tampered with by using a timer to set off airbags during some frontal collision tests instead of relying on an on-board sensor to detect a hit.
Yamaha said it had halted shipments of a sports motorcycle.
Honda, which is also due to hold a press conference later in the day, said it had found wrongdoing in noise and output tests over a period of more than eight years to October 2017 on some two dozen models that are no longer being produced.
A Toyota spokesperson added that the company is still investigating issues related to vehicle fuel efficiency and emissions, and aimed to complete the inquiry by the end of June.
Toyota shares closed down 1.8%, underperforming a 0.9% gain in the broad Topix (.TOPX) index. Mazda shares fell 3.3%.
Toyota said it had provided inadequate data in pedestrian and occupant protection tests for three production models - the Corolla Fielder, Axio and Yaris Cross - and errors in crash tests and other test methods for discontinued versions of four popular models, including one sold under the Lexus luxury brand.
It added there were no performance issues that violated regulations and customers did not need to stop using their cars.
In the Daihatsu scandal, a panel found that the unit had rigged side-collision safety tests carried out for 88,000 small cars, most of those sold as Toyotas.
