HILO, Hawai'i — A shift in the wind early Wednesday pushed a West Hawai'i brushfire southward along Mamalahoa Highway, and fire officials estimated the blaze has now consumed 2,700 acres in a path that parallels the west side of the highway for three miles.

As of 4:30 p.m. Wednesday, Civil Defense officials said, the fire was 80 percent contained, and all county roads were opened. Officials urged motorists to watch for crews still fighting the fire along roadways.

No homes were being threatened and no evacuations were in effect, they said.

Bulldozers worked overnight carving firebreaks around the western and northern edges of the fire. They are now working to widen that firebreak, said Hawai'i County Fire Chief Darryl Oliveira.

The southern edge of the fire was blocked by Waikoloa Road, and the eastern edge was mostly contained by Mamalahoa Highway, although some areas were burning west of Mamalahoa Highway.

A firebreak also was put in place around the burn area west of the highway, Oliveira said. Two major highways through the center of the Big Island remained closed because of the fire, and Civil Defense officials asked motorists to use alternate routes.

Waikoloa Road was closed from Mamalahoa Highway to the Waikoloa Stables because of fire crews working in the area and smoke hazards. Mamalahoa Highway was closed from the Saddle Road to Kaiminani Drive.

Saddle Road was reopened Wednesday for one-way traffic from Hilo to Waimea only.

"We're not calling the fire contained yet only because of the weather conditions that we're still seeing — sustained winds in excess of 20 mph," Oliveira said.

"We expect the earth to heat up, humidity to drop and wind conditions to remain constant. And we just don't feel comfortable right now calling it contained until we get past the critical part of the day, which is the hot part."

One county firefighter suffered minor injuries Tuesday afternoon when the water truck he was driving ran off Saddle Road. There was minor damage to the truck, Oliveira said.

Fire crews from the state Division of Forestry and Wildlife joined county crews and federal crews from the Army's Pohakuloa Training Area in the effort to extinguish the fire, putting a total of about 75 government firefighters on the scene.

An unknown number of private fire crews also were battling the blaze, Oliveira said.

Three bulldozers also were at work on the scene, and two county helicopters and one private helicopter were continuing to drop water on the blaze, Oliveira said.

It was not known what caused the fire, Oliveira said. It was first reported at 4:10 p.m. Tuesday in brush a mile south of Waikoloa Road near the intersection of Mamalahoa Highway.

Reach Kevin Dayton at kdayton@honoluluadvertiser.com.