A Honolulu Fire Department helicopter was slated to fly over the area Tuesday morning to make sure the fire hasn't spread.
Fire spokesman Capt. Kenison Tejada said earlier Monday that a 500-gallon portable water tank helped firefighters douse hot spots and other areas that were smoldering.
In all, the fire scorched 220 acres of brush and forest land.
The Nature Conservancy is concerned because the fire threatened native Hawaiian birds and plants in its Honouliuli Preserve.
Pauline Sato, the group's Oahu program director, said the devastation caused by the fire was significant.
Nature Conservancy officials said they expect to complete a damage estimate by the end of the week.
The blaze was blamed on children playing with fire.