Fire has damaged part of Lake Macquarie City Council's Administrative Centre at Speers Point overnight, prompting the building's closure today.
Fire alarms within the building's Customer Service Centre activated shortly before 4am, with NSW Fire & Rescue crews attending.
The building was empty at the time and no-one was injured.
Council CEO Morven Cameron said investigations were underway.
"We will work closely with NSW Fire & Rescue to determine the cause of the fire and assess damage to the building," she said.
"We've asked all Administrative Centre staff to work from home today. Unfortunately, the centre will be closed for the time being for walk-in customers."
Council's Customer Service hotline (4921 033) is currently out of action, but back-up arrangements are underway to get it back online.
"We will do everything we can to get the building and our Customer Service hotline reopened quickly," Ms Cameron said.
"We're grateful to emergency services who attended the scene and thank the community for their patience."
All other Council services outside the Administrative Centre will continue to operate as usual.
