After an "exhaustive investigation," Cargill said Wednesday that a piece of plastic recently found in an order of McNuggets in northern Japan didn't originate from its Thailand chicken processing operation.

Both Cargill and McDonald's Japan apologized last week after a piece of blue plastic about 1 ½ inches long popped up in a customer's McNuggets in Misawa, Japan.

Cargill is a big supplier to McDonald's worldwide, and the Golden Arches is a major customer for the Minnetonka-based agribusiness giant.

Cargill's investigation included "chemical analysis, microscopic third party-lab analysis and a step-by-step search across Cargill's entire production facility," the company said

"We are very confident that the plastic film in the nugget occurred outside of our production plant," Chuck Warta, president of Cargill Meats Thailand, said in a press statement.

McDonald's Japan, in a separate statement Wednesday, confirmed the results of Cargill's investigation. But the company said the possibility of the plastic entering the McNuggets during food preparation was low, and it was therefore unable to determine the object's origin, Reuters reported.

A second piece of plastic was found in McNuggets at a Tokyo McDonald's, Bloomberg News reported last week. Cargill couldn't investigate that reported incident because it could not obtain the plastic to analyze it, Cargill spokeswoman Lori Johnson told the Star Tribune.