Chinese police have launched a criminal investigation after a hospital patient died and more than 200 fell ill after eating rat poison-laced porridge.
Police had concluded the poisoning, in the north-east city of Harbin, was intentional, local officials said.
A 77-year-old woman patient died as a result of the poisoning on 9 April.
Other patients and staff who ate the porridge suffered from nausea and diarrhoea, but were said to be in a stable condition after the incident.
"The mass poisoning... was a criminal act involving the intentional use of dangerous substances," the provincial government said on its website.
Police were seeking a person or persons who placed rat poison in a kettle of water that was then used to make the morning breakfast porridge, the statement continued.
The hospital is reported to be one of the best-equipped in Heilongjiang province.
Reports of mass food poisonings are not uncommon in China. While some are deliberate, others are as a result of the country's poor record in hygiene and safety standards.
Almost 100 children in south-west China fell ill last September after eating porridge and steamed bread at a primary school.