To rub salt into the wound, McDonald’s Japan admitted Wednesday that a human tooth was mixed unintentionally into an order of french fries last summer.

The latest incident hitting the fast-food giant came a day after the company revealed two incidents involving foreign objects found in servings of chicken nuggets.

At a news conference, McDonald’s Holdings Co. (Japan) executive Takehiko Aoki and McDonald’s Co. (Japan) executive Hidehito Hishinuma admitted the company headquarters received a complaint from a customer last August who found the tooth in her order of french fries at an Osaka outlet.

The customer pointed out to an employee there that she had found a plastic-like object.

An independent investigation commissioned by McDonald’s determined it was a human tooth but was unable to determine where it came from.

The news conference in Tokyo was held in response to the revelation Tuesday that the fast-food giant had received complaints from a customer in Aomori Prefecture and another in Tokyo regarding Chicken McNuggets. In each incident, a small piece of vinyl was found.

The company also revealed another incident in which a piece of plastic 2 to 3 cm long, which the company confirmed was a broken part from an ice cream machine, was found in a sundae served at a Fukushima outlet. It injured a child’s mouth on Dec. 19.

Those incidents are still under investigation, McDonald’s said. The company said the blue, 3- to 4-cm-long object found in Aomori may have been mixed in at the company’s food supplier in Thailand during production.

McDonald’s Japan decided to stop selling chicken nuggets produced on the same date at the same factory, although 99 percent of them have already been served to customers in 14 prefectures.

For the incident in Osaka, Hishinuma and Aoki said McDonald’s considered the case closed in September as the company directly apologized to the customer, despite failing to confirm how the tooth got into its food or to publicize the incident. It was “an individual case” unlikely to occur again in other outlets and thus was not worth announcing, they said.

McDonald’s said it has no plans to stop sales of chicken nuggets that were made the same day as the one with the foreign object found at the Tokyo outlet. The company believes the 5-mm-long white vinyl did not come from the Thai supplier’s factory line.

Asked by a reporter how many similar “individual” cases occurred last year, the company officials declined to answer. They also refused to disclose the company’s standard for publicizing such incidents