A doctor shortage and patient waiting times at A&E contributed to the deaths of as many as five patients at Belfast's Royal Victoria Hospital last year, a senior medic has said.
Dr Tony Stevens, medical director of the Belfast Health Trust, which runs Northern Ireland's biggest hospital, said the patients were not treated quickly enough.
He said the patients may were very sick and may have died anyway, but that delays in treating them were considered a contributing factor to the deaths.
Speaking on BBC Radio Ulster's Nolan Show, Dr Stevens said: "Specifically, in terms of a contributory factor from people waiting longer than we would like them to be seen, we believe last year five patients in the Royal."
When asked if that was five patients who had died or who had came to harm, he replied: "Came to harm, and some, I mean, some came to harm, some died."
When he was asked how many of those had died, he replied "four or five".
Dr Stevens added: "This is something we're not happy about, that their care could have been better and their outcome might have been different, but I need to reassure the public, you cannot assume that five patients came into our hospital and, for want of waiting longer than we would want to, they died."
A doctor shortage, due to problems with both training and recruiting high calibre doctors, is an issue across Northern Ireland as well as the rest of the UK, he said.
Dr Stevens' admission comes as unions criticise Health Minister Edwin Poots for not acting to address staff concerns at the Royal's A&E department.
A damning inspection revealed on Monday that medics were under "intolerable pressure", with evidence of bullying and a dysfunctional healthcare system where not enough medics were available at times in the emergency department to properly treat patients.
Both the Royal College of Nursing (RCN) and union Unison say they had raised the problems highlighted "for months" before a major Incident was declared at the hospital last month.