Telstra has apologised for a technical issue that meant Australians weren’t able to speak to trained triple zero call takers for more than an hour.

The telco receives all triple zero calls before transferring them to local emergency services but it was unable to do so between 3.30am and 5am AEDT on Friday.

It received 494 calls during that time and was unable to transfer 148 immediately, chief executive Vicki Brady told reporters in Sydney.

She said Telstra was aware of a call to triple zero about a person who suffered a cardiac arrest and died.

“I just first offer my deepest apology to the family of that person and in fact anyone who was impacted in those 90 minutes,” she said.

Brady said she had not yet spoken to the family.

“I haven’t yet had a chance and (it is) not appropriate yet to reach out to that family but clearly we don’t yet understand how much the delay was and how much that impacted,” she said.

“But obviously it’s unacceptable if there was any delay in getting that call through.”

Victorian Ambulance Union secretary Danny Hill described the incident as distressing for everyone involved as the person who rang triple zero later received a call back after the patient died.

“It wasn’t a successful resuscitation effort, the patient passed away,” Hill told ABC Radio.

“About an hour after that, after the crew had originally arrived and had been there working on the patient, they received a phone call saying do you still need an ambulance?”

Paramedics described the situation as “complete chaos”, Hill said, as crews were dispatched to cases without knowing the details of the emergencies.

Brady said during the outage Telstra staff took down details from triple zero calls and manually sent through information to emergency services by email.

“We followed our backup process exactly as they are designed but it is clear already from our preliminary review that there are improvements that we can make in these processes,” she said.

The telco is investigating what caused its servers to not work as intended.

Communications Minister Michelle Rowland said reports of Australians unable to reach emergency services were deeply concerning.

– AAP