Firefighters have now contained 90 percent of a brushfire that has consumed an estimated 5,800 acres in the West Maui mountains since Monday, a county spokeswoman said.

But the fire flared up at about 1:30 p.m. on the Waikapu side of the perimeter, said Mahina Martin, a county spokeswoman. The flare-up was about a quarter-mile above the Kamehameha Golf Course club house, but was moving mauka and did not pose an immediate threat to structures.

Both lanes of Maui’s Honoapiilani Highway remained open today as fire officials extinguished hot spots, assisted by water drops from the fire department helicopter.

Two helicopters dropped water on the flare-up.

State firefighters from the Division of Forestry and Wildlife were working on the mauka perimeter of the fire.

The cause of the fire, which began Monday night, is under investigation.

“Our community is grateful for the hard work of our firefighters,” Maui Mayor Charmaine Tavares said. “It’s been a grueling three days for these men and women as they dealt with difficult terrain and wind conditions to protect people and properties. Fighting this fire and keeping it from increasing was no small accomplishment. It took the work of our entire community together.”