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A major Optus outage has hit hospitals, including emergency departments, as millions of customers report issues with the network.
Reports shared on social media indicate the outage is affecting mobile customers from Far North Queensland through to Melbourne, Sydney and across to Perth.
Optus Mobile customers are reporting their phones showing SOS on the signal indicator, which is a sign that your regular network is down, but that your phone has access to alternate networks in the event of an emergency call.
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Linked networks such as Dodo and Amaysim have also been affected.
9News.com.au can also confirm there are reports from Optus Home Broadband customers that their NBN connections are down, potentially indicating a deeper issue within the Optus network.
Today tech expert Trevor Long, who also contributed to this story, said the "knock on" effect of the outage could make this morning's outage the biggest in recent memory.
"Businesses that rely on Optus for payments and communication, they will be crippled this morning," he told Today.
"And this is without question the biggest telco outage we have ever seen because it spans both home wi-fi and broadband."
In a statement Optus said it was "working to identify the cause".
"Optus is aware of an issue that may be impacting some of our mobile and internet customers," the company told 9news.com.au.
"We are currently working to identify the cause and apologise for any inconvenience. In case of an emergency, customers can still call 000."
The Optus website says engineers are investigating a network fault.
Federal Communications Minister Michelle Rowland said the government was seeking information about the incident from the telco.
The Department of Home Affairs has said there is no indication the black-out is the result of a cyber-security attack.
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Melbourne's Northern Health district said on Facebook that all phone lines into its hospital campuses had been affected.
"This includes phone lines into Northern Hospital Epping, Broadmeadows Hospital, Bundoora Centre, Craigieburn Centre, Kilmore District Hospital, and Victorian Virtual Emergency Department (VVED)," they wrote.
"We apologise for any inconvenience."
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The network has messaged concerned customers.
"We're aware of an issue impacting connections for some Optus customers," it said.
"We understand connectivity is important and are working to restore services as a priority.
"We apologise for any inconvenience caused while we have the issue resolved."
More to come …
