Extra nurses had to be drafted into the emergency departments of two hospitals in Belfast yesterday evening due to massive pressure on resources.
Up to 100 people were waiting to be seen by a doctor by around 8pm yesterday in the Royal Victoria Hospital's Emergency Department (ED).
It is understood that 19 patients were waiting on on trolleys and that one man had to wait up to 11 hours to be seen yesterday.
The emergency department at the Mater Hospital was also extremely busy.
A spokeswoman for the Belfast Trust said the emergency departments were experiencing "significant pressure".
She confirmed that 15 extra nurses had to be called in across the trust – which includes the emergency departments at the Royal and Mater – to open up more beds to cope with the demand.
"They don't always just open a ward with 20 beds, they open beds in various places where they know to put people," she explained.
"For example if it is respiratory, they will open beds there. We brought in approximately 15 additional nurses to support the ED and open up an additional 20 beds in the trust."
However, the situation was brought under control later in the evening with the waiting list down to 70 people by 10pm.
While staff were under major pressure, it was not on the same scale as when a major incident was declared at the Royal Victoria Hospital in January due to a large backlog of patients at the emergency department.
At one stage, 42 people were waiting on trolleys and some ambulances were diverted to other hospitals with staff describing the situation as "horrendous".
At the time, Health Minister Edwin Poots described the incident as a "one-off".
But at the end of March, it emerged that two patients waited on a trolley in the Royal Victoria Hospital's emergency department for over 29 hours.
In February it emerged a delay in treatment at the RVH emergency department may have contributed to the death of five patients in 2013. Mr Poots announced a review of services at the RVH by health watchdog the RQIA would be carried out.
In November 2012, some emergency medicine consultants in the Belfast Health Trust raised concerns about the safety of the EDs.
Meanwhile several other hospitals confirmed last night that their own emergency care facilities had also been busy. However, none of them had to bring in any additional staff to cope.
Those who escaped the sudden influx of patients included the Ulster Hospital on the outskirts of east Belfast and Antrim Area Hospital.
Elsewhere, a spokeswoman for the Western Health Trust said the situation at its two hospitals was the same as usual for a Tuesday evening.