Nissan has halted production at all its Japan plants after it emerged vehicles rolling off the lines were being checked for quality by uncertified staff.
"We have done something inexcusable to everyone who trusted in our efforts to prevent a recurrence", Hiroto Saikawa, Nissan's chief executive, was quoted as saying said at a news conference by the New York Times.
Under transport ministry rules, all vehicles produced in Japan must pass an inspection conducted by certified technicians.
Keiichi Ishii, Japan's transport minister, said on Friday that Nissan's inspection of its assembly factories was ongoing, but it did not know how long the inspection malpractices had been allowed to continue.
Nissan said the final vehicle inspection line would now be configured as originally submitted to MLIT, consolidating all final inspection processes.
The automaker plans to reinspect 34,000 vehicles made between September 20 and October 18, 2017, and is now mulling reinspection of all unregistered vehicles now sitting at Nissan dealerships in Japan.More news: Trump Launches 'Stand for the National Anthem' Petition
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It is considering re-inspecting the unregistered vehicles at dealers throughout Japan, and submitting a noncompliance recall report for registered vehicles. The country's third-largest steel maker has admitted to falsifying data on many of its products - including aluminum and copper - for at least a decade.
The company said it had made a decision to suspend production for about a fortnight at six plants in Japan as a result of the crisis. This comes only weeks after Nissan issued a recall for all vehicles sold in the market over the past three years.
The compliance debacle is another blow for the image of the automaker. "Corrective measures" were taken by Nissan, however an external investigation found that the safety inspections done in some plants were still carried out by unqualified technicians.
Nissan said it regards the issue as critical because of the recurrence despite corrective measures taken.
During a news conference on October 2, Saikawa told reporters that the firm introduced measures to prevent any recurrence of the problem and all the vehicles assembled after September 20 had been checked by certified inspectors.
Nissan plans to publicize detailed results of its internal probe later this month.