A cluster of scrub fires near Blenheim's Wither Hills Farm Park is being treated as suspicious.
Fire Service spokesperson Brent Dunn said the three "sets" of fires broke out this afternoon and were treated as a single large blaze.
Three helicopters and seven fire crews were used to bring them under control.
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He said this evening that the fires had been put out, and a rural fire investigator was at the site.
There have been at least two other large vegetation fires in the area in the last two years.
In October 2014, a fire in a pine plantation burned seven hectares before it was contained.
Second fire in Far North
Meanwhile, two helicopters with monsoon buckets have managed to contain a fire in a forestry area in the Far North.
The fire burnt through eight hectares of harvested forestry debris on a hill face.
The Fire Service said three crews would remain there overnight to keep an eye on it.