Asia Tech Wire (June 3) -- Japanese automaker Toyota has apologized for certification irregularities.

Toyota Motor said Monday that it conducted an investigation into its model certification applications on Jan. 26 this year based on instructions from Japan's Ministry of Land, Infrastructure, Transport and Tourism (MLIT).

The automaker said that while the investigation is still ongoing, the testing methods for seven models, including some that have been out of production since 2014, were not in line with government standards.

Toyota said it had reported the issue to MLIT on Friday.

The applications for certification of the models in question involve inadequate pedestrian and occupant protection test data for three production models (Corolla Fielder/Corolla Axio/Yaris Cross), as well as crash test and other test method errors for four discontinued models (Crown, Isis, Sienta, and RX).

In the statement, Toyota apologized and said that the vehicles in question do not have performance issues that violate laws and regulations, so there is no need to discontinue use of the vehicles, but it will temporarily suspend shipments and sales of the three models currently built in Japan with immediate effect.

MLIT previously disclosed that it had received reports from five companies, including Toyota Motor, that there were irregularities in their applications for "type designation" certification necessary for mass-produced vehicles.

The regulator said it would conduct an in-house inspection of Toyota's headquarters in Toyota City, Aichi Prefecture, as soon as Tuesday.

MLIT has instructed three companies, Toyota Motor, Mazda and Yamaha Motor, which reported certification irregularities, to stop shipping a total of six models.