Firefighters are concerned following a spate of fires in Bottle Lake Forest. Photo: NZH
The last fire, near Landfill Ave about 5.15pm on Monday, spread 20m over the forest ground.
It took four crews about an hour to extinguish the blaze.
Fire and Emergency NZ has yet to establish if there is a link between the fires over the past month.
Senior officer Bruce Irvine said the risk of another fire spreading and endangering life and property increases as Canterbury continues to dry out.
He said they are working with partners to look at ways to reduce the fire risks in the area.
A police spokeswoman said an investigation is ongoing.
