Optus did not escalate at least five calls that were made to its customer service centre, including two from NSW, that informed the telecommunications company that a technical error was preventing customers from calling triple zero.

CEO Stephen Rue this afternoon confirmed that Optus had found a further three calls, additional to the two announced yesterday, where customers had complained that they could not call triple zero.

Rue said the calls were not adequately escalated within Optus’ system, meaning the telco was unaware of a major systemic failure until after 13 hours.

The inability to call triple zero affected South Australia, Western Australia and the Northern Territory between 12.30am and 1.30pm on Thursday.

A total of three deaths have thus far linked to the outage.

A fourth, the death of of an eight-month-old baby boy in Adelaide’s north, was originally linked but South Australian police have said they believe the outage is unlikely to have contributed to the infant’s death.

Today Rue said two of the calls to Optus customer service complaining of the outage came from New South Wales – although this is likely because they were situated near the South Australian border and their calls likely connected to South Australian towers.

He said welfare checks had been conducted, and that no serious injury or death had been reported as a result of the two calls in New South Wales.