Three people have died in hospital in England and three more are seriously ill after an outbreak of listeria linked to pre-packaged sandwiches, Public Health England (PHE) said on Friday.
"The cases of listeria infection were in six seriously ill hospital patients in England".
The people who died were being treated at two hospitals in the northern English cities of Manchester and Liverpool, the health agencysaid.
Three Britons have died of food poisoning after eating pre-packaged sandwiches, United Kingdom health authorities said Friday, stressing that the risk to the wider public remained "low".
Health authorities did not specify where the cases developed or how widely the sandwiches are sold.
Colin Sullivan, chief operating officer at the FSA, said his agency had taken action alongside local authorities to "minimize the risk based on the evidence so far".
"The FSA will continue to investigate how the outbreak occurred and if further steps are required to protect vulnerable groups", he added.
The cases relate to different hospitals, and it is not clear at this stage where the sandwiches were bought. The agency also said the company voluntarily halted production while the contamination is under investigation.
An investigation has been launched into the source of the infections, related to products supplied by The Good Food Chain, Public Health England (PHE) said.
This business and North Country Quality Foods, who they distribute through, have also voluntarily ceased production.
Symptoms of Listeria infection include fever, muscle aches, and gastrointestinal illness such as diarrhea.
Listeriosis is a rare infection caused by listeria which usually goes away on its own, but can cause serious problems in pregnant women or those with a weak immune system.
Public Health England noted that the National Health Service in England and Wales typically sees 166 cases of listeria infection a year.
Listeria OUTBREAK: Three deaths in United Kingdom news - what is it?