Shoppers in the US have been told not to eat any kind of spinach amid an outbreak of E.coli that has killed one person and infected more than 100.
All packaged spinach has been removed from stores
Food health experts have not yet found the bacteria, which may also have been shipped to Canada and Mexico.
Consumers were warned not to eat fresh spinach, packaged spinach or other foods containing spinach, as retailers removed the leaf from their shelves.
Infection by the E.coli bacteria causes diarrhoea and possible kidney failure.
The E.coli O157 bacterium, normally found in the intestines of people or cattle, is particularly harmful to young children and pensioners.
In the current US outbreak, one 77-year-old woman died in the state of Wisconsin, where another 17 people were admitted to hospital.
The bug is found naturally in the gut of animals including cattle, sheep, deer and goats and can be passed on by eating infected food.
Warning to customers
The US Food and Drug Administration (FDA) said that despite efforts to find and isolate the source of the bug, health experts were still hunting the E.coli infection.
The largest grower of organic produce in the US, Natural Selection Foods, pulled its packaged spinach from stores on Friday after being linked to the outbreak.
The head of food safety and security for the FDA, Dr David Acheson, said consumers should avoid all spinach, not just packaged spinach, as some retailers opened packaged leaves and sold them loose.
E.coli is particularly harmful to the young and to the elderly
"We need to get a clear message to consumers," Dr Acheson said.
"We are continuing to seek samples of spinach in confirmed cases to test for the presence of the organism, but we have not yet found it."
The FDA confirmed that spinach shipped to Canada and Mexico had been recalled, although no cases of infection had been reported in those countries.
Nineteen states have been affected by the outbreak, with the infection first reported on 2 August and the latest on 9 September.
The FDA suggested that irrigation water contaminated with cattle faeces might have been responsible for the outbreak.