At least five people who were served bleach-laced water at a Mister Donut store in Japan had to be treated by medics, the operator said Monday.
Duskin Co, a Japanese cleaning company that also operates the US fast food franchise in the country, said one of its stores in Osaka served a diluted solution of bleach as drinking water on Friday.
The mishap occurred after a worker poured the solution into a pot used for drinking water as part of the cleaning procedure at closing up time the previous day, the company said in a statement.
On Friday, another worker who thought it had been properly cleaned poured the water out for customers.
Some 12 people complained about an "unpleasant sensation", the company said.
"Two people were taken to hospital directly from the store, and three others saw doctors on their own," said a Duskin spokesman, adding none of them was in a serous condition.
Duskin operates more than 1,300 Mister Donut stores in Japan.