Three hospital patients who were part of a salmonella outbreak have died, health officials have said.
But salmonella was not cited as a contributing factor on the death certificates of two patients and the coroner's report on the third patient has not yet been delivered.
The announcement of the deaths - part of the Birmingham outbreak - come as an investigation into a national salmonella outbreak was launched.
Public Health England (PHE) said it was looking into an outbreak of S almonella Enteritidis which has affected 156 people.
Dr Mamoona Tahir, consultant in health protection for PHE West Midlands, said: "Sadly, three hospital patients who were part of the Birmingham outbreak passed away, however salmonella was not cited as a contributing factor on the death certificates of two patients and we are currently awaiting the coroner's report concerning the third patient."
Salmonella is one of a number of bacteria that can cause food poisoning.
Officials are looking into cases across Hampshire, London, the West Midlands and Cheshire and Merseyside, a PHE spokeswoman said.
The source for the West Midlands outbreak has not yet been identified, although investigations are ongoing and officials are working as part of the national outbreak control team, PHE said.
The cases occurred in "isolated clusters" over several months but officials now say they could be potentially linked.
Genetic tests suggest that the cause of illness in the 156 people could have come from a single source, PHE said.
PHE investigators are working alongside the Food Standards Agency to look into the cause of the outbreak - which may have also affected people in France and Austria.
Dr Tahir added: "Salmonella is transmitted by ingesting the bacteria, either from not washing hands thoroughly or eating infected food such as meat, eggs, poultry and milk.
"Other foods like green vegetables, fruit and shellfish can become contaminated through contact with manure in the soil or sewage in the water.
"Symptoms include diarrhoea, stomach cramps and sometimes vomiting and fever.
"Most people recover without treatment, but if you become seriously ill you may need hospital care because the dehydration (fluid loss) caused by the illness can be life-threatening.
"People already in hospital are therefore more vulnerable, due to their reduced immunity, which is why we always advise people with sickness and diarrhoea bugs not to visit patients in hospital until they have been clear of symptoms for at least 48 hours."
Dr Paul Cleary, a consultant epidemiologist leading the PHE investigation, said they are working with colleagues across PHE, at the Food Standards Agency, in local authorities and with other public health organisations in Europe to investigate the cause of this outbreak.
He said they are making "good progress and hope to have more conclusive evidence shortly".
Dr Cleary added: "We will continue to monitor the situation and if there is any further public health action necessary then we will ensure that this takes place."
Across England, experts are examinin g 55 cases in Hampshire, 32 of which have been connected with an oriental restaurant, and 33 cases in Cheshire and Merseyside, 31 of which have been linked to one oriental takeaway.
PHE are also looking at 43 cases in the West Midlands, 34 of which were connected with the Birmingham Heartlands Hospital outbreak. They are also looking at 25 cases in London.
Salmonella Enteritidis is a strain of bacteria that causes gastrointestinal illness and is often linked to poultry or eggs.
Professor Anthony Hilton, head of biological and biomedical science at Aston University, said: "If the cases are related, the next important stage will be identifying common risk factors which are associated with the infected individuals.
"This might be consumption of a contaminated food or ingredient or even a common exposure at an event or activity."
A group of diners at The Real China restaurant in Eastleigh, Hampshire, are being represented by lawyers from Irwin Mitchell, who specialise in helping victims of illness outbreaks.
A spokesman for the firm said Eastleigh Borough Council had received 70 complaints from people who had fallen ill after eating at the restaurant and 29 cases of salmonella had been confirmed.
He said: " The council's environmental health team and Public Health England are currently still investigating the outbreak and now victims have asked illness experts at law firm Irwin Mitchell to help uncover the source of their illness and gain justice for the problems they have suffered after eating at the restaurant."
Among those being represented are Timothy Taylor, 48, his wife, Bereka Sintayehu, 40, and their nine-year-old daughter and one-year-old son, who visited the Eastleigh branch of The Real China on the afternoon of July 13 after attending church.
Mr Taylor said: "Some of the food served at the buffet didn't seem to be served at the correct temperature and wasn't hot enough and the chilled food just did not feel cold.
"All of us, apart from my one-year-old son who didn't eat anything, have fallen ill after eating at The Real China and we have suffered horrible symptoms such as diarrhoea, abdominal pains and we have felt feverish.
"I had to go to see my local GP and after some tests he told me that I had contracted salmonella."
Amandeep Dhillon, a public health lawyer at Irwin Mitchell which is also representing 43 people who contracted illnesses including salmonella at a food festival in Newcastle in February and March last year, said: "We have seen on numerous occasions the severe impact salmonella can have on the victims in the short and longer term, as it can often lead to the development of long-standing health conditions, from which they may never fully recover."