An elderly man died unnoticed after lying on a trolley for 22 hours in the Accident & Emergency unit of Belfast's busiest hospital.
The man was discovered by ambulance staff who were to transfer him to another hospital.
He had been brought to the Royal Victoria Hospital's emergency department by his family.
As there were no available beds at the Royal, staff arranged for him to be transferred to a ward in the nearby City Hospital.
A full investigation is now underway including inspecting hospital notes to see just how often the patient was monitored.
Stormont Health Minister Edwin Poots said: "There are concerns around this case, and I am keen to hear a full explanation from the Belfast Trust when it has concluded its investigations."
Trust Medical Director Dr. Stevens said: "People do occasionally die. But nobody dies alone in an emergency department. Those are emotive words.
"I have no reason to believe a person died alone. What we are looking into is whether a particular patient received the level of care that is required."
The man died on March 6 but the circumstances have only now come to light.
His son, who wants to remain anonymous, said his father was talking to his partner hours before he passed away.
He said his father had been brought to hospital with a chest infection. Diagnosed with Motor Neurone Disease 18 months ago, he had been able to walk with the help of a walking aid.
"It's the biggest heartache for me and my family to have to cope with, and we are getting our information from the media," he said.
"As this story unfolds it becomes more and more tragic. I have no confidence that this investigation will uncover the truth."
He said staff at the hospital are working in "horrendous circumstances."
