The Mater hospital in Dublin is returning to normal service this afternoon after an alert this morning warned the facility was operating at full capacity.
In an email sent to managers, staff were advised of the need for special measures to be taken to relieve pressure on the hospital's emergency department.
According to the email, which was sent by director of nursing Mary Day, the Mater reached level four of its escalation plan, leading to a need to identify patients who could be discharged in order to free up beds.
This morning, 75 patients were waiting to be properly assessed at the hospital: 23 patients in the emergency department, seven in the holding bay, 18 on a ward and an additional 27 patients who had been admitted but were still needing to be seen.
The Irish Nurses and Midwives Organisation (INMO) said it was concerned by the situation at the Mater, despite things easing considerably this afternoon.
"The situation is better now with the escalation plan downgraded to level two," said industrial relations officer Albert Murphy. "But what was different about this morning was that they were actually holding ambulances as well which is unusual and a concern.
“It has been rare that the Mater has got to a level four stage. In Connolly and Beaumont hospitals there have been ongoing issues with severe overcrowding for the last few months but we haven't seen the problem happening so much at the Mater.
According to INMO figures, there are 326 patients on trolleys in emergency departments around the country today.
"We would be concerned that it's the early part of the year and the overcrowding figures are going the wrong way," said Mr Murphy.