The head of McDonald's Japan Thursday apologised after unexpected objects -- including a human tooth -- were found in the chain's food as the fastfood giant reported its first annual loss in 11 years.
The firm reported a bigger-than-expected loss of 21.8 billion yen ($186  million) last year -- 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 at a press conference in Tokyo, and bowed deeply in a common act of contrition 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.
"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."
The incidents were another public relations setback for the firm still struggling to recover from a scandal last summer when a Chinese supplier was found to be mixing out-of-date meat with fresh produce.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.