Nissan (TYO: 7201) has admitted that it falsified data from car exhaust emissions tests from factories in Japan.

The group released a statement that said it had found evidence that the exhaust emissions and fuel economy tests were carried out in a way deviating from the set tests.

“This issue came to light during the course of voluntary checks conducted by Nissan,” said the firm in a statement on Monday.

“As a companywide exercise, Nissan will continue to carry out comprehensive checks of frameworks, organizations and processes related to regulatory compliance.”

“Strict adherence to compliance is a top priority for Nissan’s management, and if issues are discovered, appropriate measures will be taken. Nissan is committed to promoting and enforcing compliance and awareness thereof in all operational area.”

The group did not say how many cars were involved in the incident or whether the falsified tests were also carried out in cars manufactured outside of Japan.

Shares in the group fell over 4.5 percent on Monday following the news.

“Nissan understands and regrets the concern and inconvenience caused to stakeholders as a result of its kanken issues last year. Proactive initiatives to prevent recurrence of such issues have led to the discovery of this misconduct, for which the company is regretful,” said the car manufacturer.

“A full and comprehensive investigation of the facts outlined above, including the causes and background of the misconduct, is underway.”

This is not the first time Nissan has had to apologise from its factories in Japan. Last September, the group admitted to having unqualified workers carry out final inspections at the end of production lines.

Volkswagen faced a similar backlash in 2015 after the group was found fitting ‘defeat’ software designed to fool emissions tests on millions of its diesel cars during the infamous emissions scandal.