A third-party investigation team discovered that workers at three factories in Japan were still performing inspections without proper certifications.

Nissan has suspended production for the Japan market after finding ongoing inspection deficiencies at three factories.Japanese regulators notified the company on September 18 of problems with worker certifications, accusing the company of allowing final vehicle inspections to be performed by technicians who were not properly registered to perform such duties.

A third-party investigation commissioned by the automaker found that the practice had continued for weeks after the government first raised concerns.

"Nissan took corrective measures at Japanese production plants by September 20 to address the issue," the company said. "By October 18, the investigation team (led by a third party) discovered that at its Oppama, Tochigi and the Nissan Kyushu plants, certain parts of the final inspection process were still being carried out by technicians not properly registered to perform those duties for vehicles for the Japan market."

The automaker has consequently halted production for Japan-market vehicles at all three locations.

Investigators determined that final inspection duties were handed off to other workers responsible for "marketability inspection" and "offline inspection."

Approximately 34,000 vehicles produced in the past year may be subject to re-inspection.