UPDATE 7.55: A NSW Rural Fire Service spokesman said the fire has been downgraded to "watch and act".
The grass fire has burnt through 60 hectares of bushland this evening, with 60 firefighters and two helicopters working to control the blaze.
The spokesman said today's hot weather combined with strong afternoon winds were likely responsible for the fire breaking out.
Though there is no longer a threat to properties, nearby residents are asked to remain vigilant.
6.15pm A fire is burning between the Old Hume Highway and the Hume Highway at Alpine.
An emergency warning is in place as firefighters and aircraft attempt to control the blaze near Ovington Road.
The grass fire has so far burnt through 10 hectares of land and is classified as ‘‘out of control’’ by the NSW Rural Fire Service.
There are a small number of isolated rural properties in the area. An emergency alert telephone warning is being sent to residents.
The Southern Highlands railway line is partially closed between Yerrinbool and Mittagong. There are limited buses from Picton and Moss Vale. Fire crews are backburning along the railway line.