Nissan Motor engineers inspecting the company's $US1.4-billion Mississippi plant reportedly traced paint flaws and scratches to the watches, wedding rings, belt buckles and bracelets that assembly workers wore on the job.

In June, the Associated Press (AP) reported, Nissan dispatched 200 mechanical, structural, electrical, chemical and materials engineers from Tokyo headquarters after a JD Power and Associates Initial Quality Study published consumer complaints about Nissan vehicles built in the United States. The study questioned 51,000 consumers who bought or leased 2004-model trucks and cars.

Consumer gripes about vehicles made at the Canton, Mississippi, factory included wind noise, vibrating brake pedals and paint blemishes, AP said.

The plant, which opened in May 2003, produces the Altima sedan, the Quest minivan, the Armada sport-utility vehicle and the Titan truck for Nissan and the QX56 SUV for Infiniti. Nissan also makes Altimas at a Smyrna, Tennessee, plant.

"The engineers walked the Canton assembly line, watched workers getting in and out of cars, studied their movements," Nissan spokesman Tom Groom told the Associated Press. "Wet paint can be mutilated very easily so the engineers walked the whole assembly line then focused on the area where the paint is still wet."

That's reportedly when the engineers spotted jewellery inflicting scratches and paint smears. He said workers have been ordered to remove their jewellery and metal accessories before taking their places on the assembly line.

AP said problems at the plant have had no apparent impact on Nissan's US sales. In July, Nissan reported its best-ever month in the United States, building on the launch of the many light-truck models out of the Mississippi plant.