Early warnings not heeded in deadly triple-zero outage

The Optus triple-zero outage lasted almost 14 hours with calls unable to be connected. (Dean Lewins/AAP PHOTOS)

Optus failed to act on initial warning signs during a triple-zero outage linked to two deaths, according to a review which has raised broader questions about the emergency phone service.

The 14-hour outage during a network upgrade in September hit South Australia, Western Australia, the Northern Territory and parts of far west NSW.