The Northern Ireland Ambulance Service is investigating whether a delayed response contributed to the deaths of eight people in recent weeks.
All eight deaths occurred between the 12 December and the start of January.
At this stage four of the deaths are being treated as serious adverse incidents.
The remaining cases are being investigated to determine whether they meet the criteria to be treated as an serious adverse incidents.
It comes as an emergency department nurse told BBC News NI he would be worried if any of his loved ones had to seek treatment as staff continued to be overwhelmed.
Stephen McKenna, who spent the Christmas period working on the frontline, described conditions as “absolutely horrific”.
Read more here.