With evacuated residents allowed back to their homes, Honolulu firefighters have shifted their focus to stopping a massive brush fire from reaching the Honouliuli Forest Reserve — home to dozens of threatened and endangered species.

Honolulu Fire Department Capt. David Jenkins said about 35 Honolulu firefighters and 13 state firefighters were maintaining and re-establishing firebreaks to prevent the fire from reaching the forest reserve.

At the same time, three private helicopters, including one from Hawaii island, were running an aerial circuit, dropping water on the blaze from a tank above Umena Street. Each circuit takes about three minutes and delivers 125 to 200 gallons of water, Jenkins said. By 3 p.m., the helicopters had been running the circuit for about six hours, he said.

The reserve, along the windward side of the Waianae Mountain Ridge, is home to more than 90 rare and endangered plant and animal species, according to the state Department of Land and Natural Resources. The endangered Oahu ‘elepaio bird and endangered “singing” kahuli tree snail also live there.

About noon Sunday, firefighters allowed residents in the Umena Street area to return to their homes after the lower perimeter of the fire was contained, Jenkins said. Firefighters planned to maintain a fire watch along the area overnight.

Jenkins said the blaze charred about 800 acres and remained uncontained in the upper slopes.

The fire, first reported around 3:30 p.m. Friday, prompted the evacuation of about 20 houses on and near Umena Street and 20 cabins and other structures at Camp Timberline. One home sustained minor structural damage.

At one point on Friday, about 100 of the 300 firefighters on duty were responding to the fire, Jenkins said.

On Saturday, 20 fire companies and 60 firefighters continued to battle the fire as it moved up Palehua Road. Two police helicopters also assisted in the fight.

Investigators confirmed Saturday that the massive brush fire was accidentally started by two young boys playing with a lighter they had found.

“We regret what has happened,” said the boys’ father, Troy Wright, in a prepared statement. “Our children realize the consequences of their actions. We want parents to realize this can happen to anyone and how important it is to discuss fire safety with their children.”