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TOKYO (Reuters) - Nissan Motor Co 7201.T said Japan sales of new passenger vehicles probably fell by half in October from a year ago after the discovery of improper final inspection procedures at its domestic plants caused it to suspend some production.

The Japanese automaker found last month that uncertified technicians had been carrying out final inspections of vehicles for decades. That has prompted it to recall 1.2 million vehicles, including all passenger cars it produced for sale in Japan over the past three years.

The plants will resume production once the final inspection procedures have been brought in line with transport ministry requirements and the ministry has approved the measures, a spokesman for the automaker said.

Nissan has completed those measures at one of its assembly plants and expects to have made similar changes at five other plants by the end of the week, he said.

Tightened procedures will mean only certified inspectors will be allowed into the final inspection area, and there will be regular checks that inspections are carried out properly.