Australia's media regulator has begun its investigation into what caused an Optus triple-0 outage that has been linked to four deaths, as Communications Minister Anika Wells warned there would be consequences for the telecommunications sector.

Last week's outage primarily impacted South Australia, Western Australia and the Northern Territory and resulted in the failure of more than 600 emergency calls over 13 hours.

Optus chief executive Stephen Rue revealed on Friday that three people had died, describing what had occurred as "completely unacceptable".

Australian Media and Communications Authority (ACMA) chair Nerida O'Loughlin on Monday said that her agency was not notified of the outage until after it was resolved, which is counter to the usual processes.

For significant outages, sh

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