The blaze near Pontsticill Reservoir is being fanned by strong winds and has been burning since early on Monday morning. At its height the fire was being tackled by more than 20 fire fighters.
South Wales Fire and Rescue took the decision to remove crews from the area amid fears for the safety of crews working in the dark – a spokeswoman said it was hoped the blaze would burn itself out.
The fire service reported that it has attended 180 grass fires since March 1st and 54 deliberately started grass fires over the weekend in South Wales, 40 on Sunday alone.
The fire service said a plan to contain the blaze was being put in place in association with Natural Resources Wales.