The telco receives all Triple Zero calls however it was unable to then transfer them on to emergency services on Friday for an unknown reason.

“An issue early this morning affected calls and associated data being transferred to emergency service operators,” the company said in a statement.

“It was fixed within 90 minutes.

“Our team of call takers switched to our backup process, which meant the details of callers were sent manually to emergency services to be called back.”

The telco said it is investigating the cause of the problem and closely monitoring the system.

The issue occurred between 3.30am-4.45am on Friday, according to Triple Zero Victoria.

“Throughout the disruption Telstra provided Triple Zero Victoria with the details of callers who were responded to as a matter of urgency,” the service said in a statement.

Paramedics described the incident as “complete chaos”, Victorian Ambulance Union secretary Danny Hill said.

“We’ve had issues with incorrect routing of calls from Telstra to the wrong control room, particularly in cross border areas,” Mr Hill told ABC radio.

He claimed crews were dispatched to cases without knowing the details of the emergencies.

Mr Hill said one particularly distressing case involved a person who rang Triple Zero to report someone having a cardiac arrest, who later received a call back after the patient had died.

“It wasn’t a successful resuscitation effort, the patient passed away,” Mr Hill said.

“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?”

Mr Hill said it was upsetting for everyone involved.

“Quite distressing for the call taker, because what they were tasked with doing was calling up a lot of the cases where they think there may have been a delay to see if they still needed an ambulance,” he said.

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

“The Federal Government has urgently sought information from Telstra as Emergency Call Person to understand the full extent and impact of the outage,” a spokesperson for the minister said.

Communication Workers Union representative Sue Riley said Telstra’s call takers captured as much information as they could before emailing information to emergency services.