Holiday makers are being urged to clue up on guidelines before visiting pest-free islands.
A camp fire was lit in front of a total fire ban sign on Burgess Island in the Hauraki Gulf. Further signs of camping, which is also prohibited, have been found on the island since the beginning of the year.
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Department of Conservation (DoC) Great Barrier Island operations manager George Taylor told Newshub it endangered breeding seabirds.
"We just cannot believe the idiocy of some people to light a fire on an island that contains a lot of native and endemic species."
Mr Taylor says the fire could easily have spread with devastating consequences and guests to the island should have known better.
"Most of these pest-free islands do come with some guidance on how to visit the place, definitely lighting fires is not acceptable."
DoC is urging people to avoid activities that could disturb native species, such as camping and lighting fires.
"These pest-free islands are preserved for the good of the many species that preside on them. It's up to us to actually try and protect them as best we can," Mr Taylor said.