The transport ministry searched the headquarters of Subaru Corp. on Wednesday after the automaker submitted a report saying it had rigged mileage and emissions data for new vehicles at one of its plants.
The ministry will question senior officials of the company about the report and determine what measures to take.
The company altered fuel economy and other data in the final inspection process for new cars at the plant in Ota, Gunma Prefecture.
The report released April 27 said the data falsification was conducted systematically on the orders of the head of inspection staff but that managerial staff were unaware of the misconduct.
Subaru said the malpractice, which began as early as 2002, affected 903 units across all of its nine models including the Forester sport utility vehicle, as well as Toyota's 86 sports car, which Subaru manufactures.
The revelation was yet another black mark against the carmaker, which admitted late last year that unauthorized staff had conducted inspections of new cars, triggering a massive domestic recall.