The head of McDonald's Japan on Thursday apologised after unexpected objects -- including a human tooth -- were found in the chain's food as the burger giant reported its first annual loss in 11 years.
The firm said it would lose a worse-than-expected 21.8 billion yen ($186 million) for 2014 -- reversing a year-earlier profit -- as sales plunged in the wake of the embarrassing discoveries.
The unit's Canadian chief Sarah Casanova said the poor results marked a "harsh evaluation" by wary customers when she appeared at a press conference in Tokyo. She bowed deeply in an act of contrition common for executives in Japan.
"I would like to sincerely apologise once again for all of the great anxiety and concern," she told reporters.
A human tooth was found in some french fries sold at an Osaka outlet last year, the firm admitted in January.
McDonald's said there were no employees missing a tooth at the outlet and it believed there was a very low possibility of contamination at the US factory that had shipped the chips.
Two days later, a Japanese woman claimed to have discovered what was later identified as "dental material" in a McDonald's hamburger from northernmost Hokkaido in September.
Japanese media reported several other cases of contamination, including a piece of metal in a pancake.
Casanova said she was assembling a "task force" to study how to prevent future contamination at more than 3,000 restaurants across the country as January sales plummeted 39 percent from a year ago.
- 'Whatever it takes' -
The firm gave no estimate for earnings this year.
"When we received claims from customers we took each of them seriously," Casanova said.
"Regrettably, we were not able to always identify the cause of the issue...We will have to work harder than ever to regain the confidence of our customers. We'll do whatever it takes."
McDonald's has been operating in Japan since 1971.
Japan generally has a good record on food safety, and its consumers are used to high standards.
Occasional blunders can prove costly to reputations, and firms that have fallen foul of shoppers have discovered the impact can be long-lasting.
The incidents were another public relations setback for a firm still struggling to recover from a scandal last summer when a Chinese supplier was found to be mixing out-of-date meat with fresh produce.
Late last year the company had to airlift an emergency supply of french fries from the US after a chip shortage resulted in rationing at restaurants across Japan.
Labour disputes on the US West Coast had bunged up the export chain, leaving Japanese firms scrambling to secure fresh supplies.
Last week, McDonald's replaced president and chief executive Donald Thompson after the company turned in another poor quarter of sales and earnings.
The decision came after McDonald's reported a 2.4 percent decline in revenues last year and a hefty 19-percent drop in earnings per share, with falls in store traffic in all regions -- the chain has 36,000 outlets in over 100 countries.
Shares of the burger giant's Japanese business fell 1.03 percent to 2,603.0 yen in Tokyo on Thursday. The stock has tumbled about 12 percent from its highs in the summer as the Chinese factory scandal hit.