McDonald's Corp. officials in Japan have bowed deeply to apologize for a human tooth and plastic pieces found in the burger chain's food.

They told reporters Wednesday the objects were found by customers, including a child whose mouth was injured by a piece of plastic in an ice cream sundae in December. The fragment had fallen into the dispenser while being assembled.

In another case, a customer who bought a Big Mac set in August last year found a tooth in the fries. McDonald's said none of its employees at the outlet or its suppliers had lost a tooth, and there were no signs the tooth had been fried.

It was still investigating how the tooth and plastic, in two other separate cases, entered its food.