Telstra is investigating the cause of a fire in its Warrnambool exchange in south-western Victoria that has knocked out fixed and mobile voice and internet services for up to 60,000 users.
A spokesman for the carrier, James Howe, told radio station 3AW that the fire broke out about 4.30am (Thursday), with technicians only able to get their first look at the damage from 8am.
Victoria's Country Fire Authority said five crews had fought the flames and that it had taken 1.5 hours to bring the fire under control.
"The exchange sustained around 60 percent damage," the authority said. "The cause of the fire will be investigated."
It could take "a number of days" for services to be restored, Howe told 3AW.
"A number of communication technicians are onsite and an assessment of the damage is underway," Telstra said on its network status page.
"We have a team of experts who will work around the clock monitoring our network and co-coordinating our restoration efforts to connect all of our customers again as quickly as possible."
The Standard carried a number of photos of the damage to the exchange, showing part of the building's roof missing.
The fire has hit services provided by Telstra, Optus and many large internet service providers, as well as banking services such as ATMs.
Optus reported on Twitter that fixed line services in Warrnambool are "currently unavailable", and there was no estimation available for restoration.
ISP Internode noted that "ADSL and NodeLine services across multiple exchanges, in the Warrnambool area of Victoria, may be unavailable", with similarly no restoration indication.
"Structural engineers are now onsite assessing the integrity of Warrnambool exchange in conjuction with emergency services personnel," it noted in a technical advisory.
"Techs have managed to gain access to some areas of the building."
Telstra noted via its Twitter account that it had sent several portable exchanges to the site to provide some temporary coverage.
These included its Satellite Cell on Wheels (SatCOW); Cell on Wheels (CoW), which is a portable mobile base station; and its Mobile Exchange on Wheels (MeOW), a portable ADSL2+ exchange.
"2xSatCOW just arrived at Melb Airport, being driven to #Warrnambool providing the township with mobile service ASAP," the carrier noted at 5pm AEDT on Thursday.
Telstra noted its technicians were "working to restore power" late into the night.
Telstra said it had managed to get 2G sites working at Edenhope, Coleraine and Port Fairy.
Update, 23/11 7.30am: Telstra has restored mobile phone services to Hamilton.