The fire at Richmond Vale is being controlled by fire crews.
Fifteen trucks and two waterbomb helicopters were on scene battling the 35 hectare blaze.
A Rural Fire Service spokesman said property protections were in place due to strong winds that had pushed the fire towards the Hunter Economic Zone.
Spot fires also broke out near the Richmond Vale Railway Museum.
The spokesman said he expected back-burning to continue into Tuesday evening.
A fire has broken out at Richmond Vale, between Mulbring and Kurri Kurri, on Tuesday afternoon.
The Rural Fire Service reported the blaze had tore through about eight hectares of land off the Tomalpin Link Firetrail.
Rural Fire Service firefighters are on scene. It is believed that strong winds are impacting control of the fire. Northwesterly winds of 20 to 30 km/h were forecast for Tuesday.
The incident was at advice level just before 1.30pm, meaning a fire has started, but there is no immediate danger. Residents are advised to stay up to date in case the situation changes.
Updates are available at www.rfs.nsw.gov.au/fire-information/fires-near-me.