Fire and Emergency NZ Incident Commander Dave Berry said the rural crews are systematically digging out "deep-seated hotspots, where the roots of gorse plants and other vegetation are burning underground and can reignite surface fires".
"Career firefighters have also been at the scene today, extinguishing hotspots within farm sheds and associated structures.
"There has been no rain on the fire ground today and temperatures have been hot, but so far conditions have been relatively calm."
Berry said firefighters will remain at the scene near the Selwyn River overnight and fresh crews will be back tomorrow.
Fenz continues to monitor the site of a second roadside fire on SH1, a few kilometres to the south of the other blaze near Dunsandel which is associated with the main fire.
"Firefighters were dealing with hotspots there this morning.
"Two fire trucks and two tankers are currently at the site of another vegetation fire on Pound Rd, which was reported at 1.40pm.
"A restricted fire season is in place for Canterbury, Mid-South Canterbury, meaning that a permit is required to light outdoor fires.
"Fire and Emergency also asks people planning activities like grinding, welding or anything else that could generate a spark to take some simple precautions that will reduce the risk of starting a fire.
"That includes planning activities for early in the day when conditions are generally cooler and calmer, staying away from long grass, and having water at hand to extinguish any sparks."
