The HSE has said the emergency department at Sligo University Hospital (SUH) is extremely busy with high numbers of people attending who need to be admitted to hospital for ongoing treatment.
There were 28 patients on trollies in the emergency department this morning.
The hospital has advised patients who attend the ED for routine and non-urgent treatment that they will experience "very long waiting times".
All available beds in the hospital are in use and the HSE has said patients waiting to be admitted from the emergency department to a ward bed will also face a long wait.
The HSE said in a statement that "every effort" was being made to discharge patients who are ready to go home so that beds become available for those who need to be admitted.
Those who require emergency care are encouraged to attend the emergency department.
SUH said it acknowledges that the delays are very difficult for patients and their families and it apologised for the inconvenience and distress caused.
It said the hospital is committed to treating everyone who presents at the emergency department.
"People who are seriously injured or ill are assessed and treated as a priority and those who do not require urgent care may be waiting longer," it said.
"We continue to request that people only attend the emergency department at the hospital if it is an emergency.
"We ask that people attend their GP or out of hours service in the first instance if possible."
