Firefighters from the Department of Land and Natural Resources battled a wildfire in the Waianae Kai Forest Reserve on Saturday, with help from helicopters that dropped water on the steep slopes.

DLNR spokeswoman Deborah Ward said her department sent 16 ground personnel and used contracted helicopters to fight the fire in the lower part of the reserve.

“It’s steep terrain, but it’s not in the upper areas of the Waianae Mountains,” Ward said Saturday morning. “As of yet, it’s not likely that native or endangered species are being affected, but we’ll have to see what happens.”

She said about 400 acres in the forest reserve were affected by the fire. The foliage in the area consists of dense guinea grass, koa haole, silk oak and other non-native species.

The blaze broke out Thursday night and has scorched an estimated 2,000 acres in Waianae Valley. Fed by gusty wind on Friday, it threatened homes and engulfed an auto parts business, torching hundreds of used cars on the lot. But Honolulu Fire Department personnel managed to push it back.

With the fire contained to the forest reserve, DLNR’s Division of Forestry and Wildlife took the lead Saturday. The Honolulu Fire Department shifted to a support role, offering its tender vehicle for refueling and maintenance of helicopters, and a water tank, but not deploying its own firefighters on the ground.

The Fire Department reported that the lower, populated section of Waianae Valley was safe.

“The lower area is secured,” said Capt. David Jenkins, public information officer for the Honolulu Fire Department. “It’s totally contained. Everything down in the valley is OK.”

“If there is a need or there are concerns, people can still call the Honolulu Fire Department,” he added. “We will go out and assess and do what’s needed to keep the community safe.”

Jenkins said investigators have not determined what triggered the fire, but added that the weather whipped it up.

“The winds were a definite major factor in regards to this,” he said. “It caused the fire to quickly spread and hampered firefighting efforts in the initial stages of fighting the fire.”

The last major fire in the upper valley burned 1,200 acres in June 2012, including 400 acres of forest reserve.