Subaru had uncertified staff conducting vehicle inspections at a pair of factories for decades, media reports said Friday, as it became the latest Japanese firm hit by scandal.
An internal investigation found the practice has been going on for around 30 years in an apparent misconduct crisis similar to the one at bigger rival Nissan, according to Kyodo News agency and other Japanese media, which cited a company insider and other unnamed sources.
The reports dented Subaru shares, which fell more than 3.0 percent in early trading before ending the morning session at 1,996 yen ($17.50), down 1.93 percent.
A Subaru spokesman in Tokyo declined to comment on the reports and said the carmaker is "still conducting an internal investigation" into the matter.
A Subaru executive said some inspections at the two plants northwest of Tokyo were being performed by workers who were still being trained for the job and had not yet been certified, Kyodo said.
"This practice has been carried out for more than 30 years," the executive was quoted as saying.
Up to 300,000 vehicles could be affected, the Nikkei business daily said.
Subaru trails far behind larger rivals Toyota, Nissan and Honda, selling about one million vehicles annually.
The news comes after Nissan said earlier this month it would recall 1.21 million cars in its home market after it emerged that unqualified staff were performing final checks on vehicles before they were shipped to dealers and consumers.
That admission came as major Japanese steelmaker Kobe Steel said it has systematically fabricated strength and quality data on some products shipped to hundreds of clients.