South Australia’s health department is investigating what caused a nine-hour outage to its notorious EPAS system across three major Adelaide hospitals on Monday night.

Between 3pm and midnight Adelaide time, the critical medical records system became unusable or completely unavailable at the Queen Elizabeth Hospital, the Repat Hospital, and the Noarlunga Hospital. The three sites are the first to be hooked up to the electronic patient administration system (EPAS).

SA Health CIO Bill Le Blanc today apologised for the glitch, which he said was caused by a rogue piece of software that suddenly began to consume all the compute resources assigned to EPAS.

“Out of the many hundreds of software components that make up the system there was one small piece that had malfunctioned and it consumed the bulk of all the computer resources that sit behind the scenes," he said.

“That then deprived those resources from the end users, meaning they were experiencing much slower response times."

It took a team of technical experts nearly 10 hours to find the issue and rectify it.

“EPAS is an incredibly complex system made up of many many moving parts, so it took us some time to narrow it down,” Le Blanc said.

He denied the department and its EPAS vendor Allscripts had mistakenly under-provisioned resources for the 10-week-old implementation of the system in the Queen Elizabeth Hospital.

Elizabeth Darbars from SA’s Nursing and Midwifery Federation told ABC radio staff were unable to access patients' clinical histories during the outage.

But Le Blanc and Health Minister Jack Snelling insisted that the state’s hospitals had layers of backup in place to make sure doctors can still access patient information when things go wrong.

“We have backup systems and backup systems for our backup systems,” Le Blanc said.

“In every area of the hospital there are redundant back up computers … and they are updated every 15 minutes with the latest information on patients that are in the hospital.

“That information absolutely was available last night.”

Allscripts and the department will now launch a deeper review into what caused the software malfunction in the first place to remove the bug before EPAS is installed in the much larger new Royal Adelaide Hospital next year.

EPAS is already controversial in SA’s political and clinical circles, after the $422 million implementation hit usability issues and significant delays that threaten to eclipse budgeted savings targets.