Police are investigating a technical fault with the 111 system which prevented people from reaching emergency services in the early hours of Sunday morning.
The nationwide fault affected people trying to get through between midnight and 12.45am. Callers received an automated message saying the system was overloaded and could not proceed any further.
Acting national manager for Communication Centres, Inspector Mal Schwartfeger said the fault was with the Police system rather than Spark.
The Spark initial call answer point identified the issue and alerted Police. Standard business continuity processes were put into practice immediately.
"Police went to the backup system and all available call takers were placed on phones to reduce the queue. It took 35 to 40 minutes to clear the backlog of calls."
Police remained on the backup system until the main system was restored and operational at 2am.
"We apologise to those people who were unable to access emergency services and can assure people that the system has been restored to normal service".
"We believe a number of callers were affected, however more work needs to be done before we know the exact number. We do know that some callers called back on numerous occasions"
Further investigation is underway to ascertain exactly what caused the fault.
"Any fault with the 111 system is of concern because of the risk to people who may be in life-threatening situations. We will be taking any necessary steps to ensure the fault does not occur again"