Three hospital patients have died after eating pre-packaged sandwiches linked to a listeria outbreak.
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.
Cases of listeria infection were found in six seriously ill hospital patients.
Those who died were at Manchester University NHS Foundation Trust and Aintree University Hospital NHS Foundation Trust in Liverpool.
Dr Nick Phin, deputy director at the national infection service at PHE, said: “Our thoughts are with the families of those patients who have died.
“We, along with the Food Standards Agency, colleagues in local authorities and the NHS have worked quickly to determine the likely cause of this outbreak and taken action to reduce the risk to the public’s health.
“To date, there have been no associated cases identified outside healthcare organisations, and any risk to the public is low.”
The first case showed symptoms on April 25 while the most recent case was reported on May 15, a PHE spokeswoman said.
Sandwiches and salads were withdrawn on May 25, as soon as a link with the cases was suspected.
It is understood that some of the products were sold at hospitals while others were given to patients.
The Good Food Chain, which supplied 43 NHS trusts across the UK, has voluntarily ceased production.
The business was supplied with meat produced by North Country Cooked Meats, which has since tested positive for the outbreak strain of listeria and also stopped production.
Listeria infection is rare and usually causes a mild illness in healthy people.
However it can have more serious consequences among those with pre-existing medical conditions, pregnant women and those with a weak immune system.
Dr Colin Sullivan, chief operating officer at the Food Standards Agency (FSA), which is helping with the investigation, said: “Our sympathies are with the families of those patients who have tragically passed away.
“We have taken action along with local authorities to minimise 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.”
A spokesman for North Country Cooked Meats said: ““At this stage the company is currently cooperating fully with the environmental health and the FSA in their investigations and a further statement will be issued in due course.”