Nissan has admitted that it has uncovered falsified data from car exhaust emissions tests at most of its Japanese factories.
The firm did not disclose how many cars were involved, but said emissions and fuel economy tests had "deviated from the prescribed testing environment".
Nissan pledged there would be a "full and comprehensive investigation".
It added that "appropriate measures" would be taken to stop any future recurrence.
Nissan has not revealed how many cars were involved in the altering of data, or if it involved vehicles manufactured outside Japan.
The company said it had rechecked "reliable" data and confirmed that all vehicles except the GT-R sports car conformed to Japanese safety standards. It did not explain why the GT-R had been excluded.
Nissan’s shares fell more than 4.5% on Monday after the company alerted investors that a statement on exhaust emissions was imminent.
Last year, Nissan recalled 1.2 million vehicles in Japan after regulators said safety checks did not meet domestic requirements.
The admission by Nissan comes after a huge scandal involving diesel emissions test cheating by Germany’s Volkswagen.
Last month, VW was fined euro1bn (GBP880m) by German prosecutors for selling more than 10 million cars between mid-2007 and 2015 that had test-cheating software installed.
