Michael Patterson, a Telstra spokesperson, told iTnews that 22 sites had been impacted by the power outage, with seven of those sites losing power.
Patterson said that businesses' telecommunications, including their landlines, may have been affected by the outage.
Five of those sites had power restored within two hours, using either generators or topping up of battery power, Patterson said.
“We've got a global operations centre so, rather than customers having to contact us, we are aware of the impact, including battery power,” he said.
“As soon as the mains power had an outage we were aware of the impact and we put resources [in place] to resolve some of those issues.”
Patterson added that it could sometimes be difficult to get generators to some customers, for example if they were on an upper-level of a high-rise building.
Telstra was working closely with customers and the energy provider to identify priority sites and work in a cooperative way, he said.
The power outage was caused by a fire that broke out in an underground cable tunnel Monday evening, according to a statement issued by EnergyAustralia.
High voltage cables passing under the Darling Park office complex on Sussex Street were damaged.
“EnergyAustralia repair crews were only able to access the fire scene after being given the all clear around 11pm last night, when carbon dioxide gas used to extinguish the electrical fire, had dispersed,” it stated. “Through the morning, cables have been rejoined and power restored to most of the affected city buildings.”
EnergyAustralia did not yet know the cause of the fire, according to the statement.