Image copyright AFP Image caption McDonald's has admitted three incidents of food contamination in Japan

McDonald's has apologised after a human tooth was found in a portion of fries in Japan last year.

A customer complained after making the discovery at an Osaka outlet in August. McDonald's said an independent probe had found it was a human tooth.

The firm has also admitted that a piece of plastic was found in an ice-cream sundae, and a piece of vinyl was discovered in chicken nuggets.

McDonald's executives said they would work to eliminate such incidents.

The fast-food giant has faced a number of problems in Japan recently, including a shortage of fries that forced them to import from the US.

The firm has now admitted three cases of food contamination in the past year:

A tiny piece of plastic in an ice-cream sundae injured a child's mouth in the city of Koriyama in December

A piece of vinyl was inside a chicken nugget sold in the city of Misawa last weekend

A human tooth found in a portion of fries in Osaka last August

At a news conference on Wednesday, Hidehito Hishinuma said an examination of the tooth determined it had not been cooked.

"We were not able to discover how it got in the food," he said.

The woman who found the tooth had earlier claimed that the store manager had told her the tooth had been fried.

McDonald's executives defended the overall quality of McDonald's food and said the incidents were isolated cases.

They said they were aiming to make sure such incidents never happened again.