Optus is pledging to fully investigate a 10-hour triple-zero outage, accepting responsibility for a number of breakdowns during which at least four people died.

The telco’s chief executive says an independent investigation will be conducted after admitting the outage was caused by a botched firewall update to the system.

Stephen Rue admitted Optus had been contacted by the telecommunications industry ombudsman about two complaints of people trying to inform the company about the outage.

“Early review suggests that we had not handled these calls as would be expected,” he told reporters in Sydney on Saturday.

“Optus will be appointing an independent person to lead a review into this entire incident from every aspect, I hope to confirm that person in coming days.”

Optus was unaware of Thursday’s outage until being notified by a customer about 1.30pm after the emergency service line was unavailable for 10 hours, Rue said.

The update was cancelled and access to the emergency line was restored, he said, but not before at least three people had died during the outage after hundreds of people were unable to reach emergency services.

The deaths included an eight-week-old infant in Adelaide. A 68-year-old woman in Adelaide and 74-year-old man in Perth also died while another West Australian death was confirmed on Saturday night.

WA Police have told Optus they believe the person likely tried to call triple-zero for help.

The telco said it would work with authorities to understand what happened.

Rue pledged to give daily updates as more information about the grave incident came to light and said Optus accepted full responsibility for the problem.

Optus was slammed by the South Australian premier for not passing on adequate information to the state’s police after the outage, hampering locating people who needed help.

SA Premier Peter Malinauskas described the lack of information from Optus as “bewildering”. Photo: AAP

Premier Peter Malinauskas said it took a call from him to the Optus CEO before the problem was fixed.

“The lack of information flow from Optus to the South Australian government’s appropriate authorities is somewhat bewildering and it raises a lot of questions,” he said.

Federal Communications Minister Anika Wells slammed the telco for failing to heed the recommendations of a review into a November 2023 outage where customers were also unable to contact triple-zero.

Rue defended not publicly revealing the outage until Friday night in a snap press conference more than a day after the problem was identified and rectified.

He said Optus was focused on determining the facts and conducting welfare checks before informing governments and the public.

Communications Minister Anika Wells said the triple-zero outage was unacceptable. Photo: AAP

Wells questioned how the incident could occur again nearly two years after a similar outage after which a review identified problems Optus should have addressed.

“We’re disappointed that it’s happened again, no triple-zero outage is acceptable and this will be thoroughly investigated,” Wells said.

“Many of the things that happened in this outage are failures to implement some of those recommendations, including alerting the public or emergency services authorities.”

—AAP