The youths, aged 13 and 14, have been referred to Youth Aid.
The small vegetation fire on Cape Wanbrow, below Lookout Point, was cause for concern, Otago Rural Fire Authority duty officer Jason Dodds said yesterday.
At least 20 firefighters - from Oamaru, Weston, Kakanui and Waitaki - responded to the fire that covered 25m by 15m in a gully crossed by walking tracks.
''It's one of those calls we don't actually want to hear - when the cape's on fire,'' Mr Dodds said, once the fire was under control about 3pm.
''You might see it as a little bit of overkill, but we just didn't want it to get started; if it got going we could have been here at this time tomorrow still and then there would be a lot more properties at risk.''
In the westerly winds two smaller spot fires flared up about 120m from the original fire.
By the time rural fire crews were mopping up the fire, the wind had changed, blowing 28kmh from the northeast, which would have put homes at risk.
Oamaru Volunteer Fire Brigade Chief Fire Officer Steve Couper said the fire was ''potentially very dangerous''.
''When you start getting spot fires you've got extreme weather conditions,'' Mr Couper said.
''It just shows you how dry it is out there.
''It is very dry and there's still a lot of fuel up there.''
Mr Couper, who acted as safety officer yesterday, said there was ''very little damage if there was any'' to the recent native seedlings planted along the cape.
An investigation into the cause of the fire was under way.
