HILO, Hawai'i — A brushfire that started Saturday under suspicious circumstances in the Mana Road area of the Big Island has burned an estimated 2,600 acres, and federal, state and county fire crews worked yesterday trying to contain the blaze.

Big Island Deputy Fire Chief Glen Honda said helicopters dumped water on the fire in an inaccessible area on the slopes of Mauna Kea yesterday. Firefighters were trying to protect a cabin in the isolated area.

Thirty-five firefighters and four helicopters battled the blaze, which was first reported as two separate brushfires at 2:10 p.m. Saturday in Hakalau, near Mana Road.

The fires later merged to form a single 20-acre blaze, and burned about 600 acres by Sunday evening. Most, or all, of the pastureland involved is owned by the state Department of Hawaiian Home Lands, Honda said.

Crews used bulldozers to cut fire breaks and conducted backburning along Mana Road to contain the fire and keep it from moving makai, but the fire continued to burn yesterday mauka of Mana Road.

County fire crews were working with a crew from the Pohakuloa Training Area and staff from the state Division of Forestry and Wildlife to try to contain the blaze, Honda said.

Firefighters remained at the scene last night to suppress any flare-ups, said Neil Gyotoku, spokesman for Big Island Civil Defense.