Update 3pm:
Half the customers affected by an outage in the area around Newcastle West and Wickham have had power restored.
Ausgrid said just before 3pm that the remaining properties impacted by the outage would have access to electricity again within an hour.
It has been confirmed the outage was caused by an underground cable being dug up at a private work site.
Thursday's incident was the second time this year that construction work in Wickham hit underground power lines causing outages for at least 900 customers.
Investigations continue into how the contractors came into contact with the underground cable.
"Ausgrid has an extensive network of underground electricity cables and coming into contact with them can cause serious injuries or prove fatal," Ausgrid said in a statement.
"Anyone working near the electricity network needs to make sure they know where underground electricity cables and utilities are before they start any excavation works.
"We advise all contractors to contact Dial Before You Dig - which is a free service supported by Ausgrid and other major service providers that supplies plans of where electricity, water, gas and telecommunications cables and pipes are located so you know whether it is safe to dig.
"NSW legislation requires people who are planning excavation work to obtain copies of underground electricity cable plans from Dial Before You Dig.
"Dial Before You Dig can be contacted by calling 1100 (freecall) or online at 1100.com.au."
Earlier report:
NEWCASTLE'S western CBD has lost power on Thursday in an outage affecting traffic lights through the busy CBD.
Roughly 900 customers in parts of Newcastle West, Tighes Hill and Wickham have lost power. The outage is centred on the Hannell Street area.
Power dropped out in Honeysuckle shortly after 1pm, with traffic lights affected by the outage.
Ausgrid said shortly before 1.30pm there was no estimate on when power would be restored.
The believed cause is an underground cable being dug up at a private work site in Wickham or Maryville, an Ausgrid spokeswoman said.
Light rail services are running.
