Telstra has begun restoring network services across the nation after experiencing an hours-long mobile outage, with the telco saying it has not determined the root cause.
"We are progressively restoring mobile services and we anticipate returning to normal soon. We believe the incident has impacted a proportion of traffic for voice and data across the country," a Telstra spokesperson told ZDNet in a statement.
"The cause of the incident is yet to be determined, but at this early stage, we understand we have had a problem with the part of the network that allows phones to register and therefore make calls and use data.
"We apologise to our customers for the inconvenience caused."
The outage began around 5pm AEDT on Thursday, and was experienced across the country, with smartphones stuck on "SOS only" or "no service", unable to connect to either data or voice services.
While 3G services are now working intermittently, 4G services do not appear to be back online as of 9.30pm AEDT.
Telstra last month likewise experienced a similar outage across prepaid and post-paid mobile services, which resulted in the telco gifting all customers with free unlimited data on February 14 to provide compensation for the outage caused by "embarrassing human error".
Last month's outage took down 2G, 3G, and 4G services across the country for several hours.
Telstra chief operating officer Kate McKenzie previously revealed that February's outage had been caused by an incorrect procedure being followed after one of the telco's 10 nodes was taken down to be repaired.
"Our mobile network is set up with a number of major connection points -- what we call nodes -- around the country, which our customers connect to. These nodes are the equipment that essentially manage the flow of voice and data traffic across our mobile network. The outage was triggered when one of these nodes experienced a technical fault and was taken offline to fix," McKenzie explained.
"This normally wouldn't impact services, as we have processes in place to make sure any customers currently connected to a node are transferred to another node before it is taken offline. Unfortunately, on this occasion, the right procedures were not followed and this resulted in customers being disconnected and consequent heavy congestion on other nodes as customers attempted to reconnect to the network."