HILO, Hawai'i — A brushfire that burned an estimated 8,900 acres Sunday and yesterday near Waikoloa on the Big Island may have been deliberately set.

The fire was the largest Big Island brushfire so far this year, and cut access to the primary highway between Waimea and Kailua, Kona, for 10 hours yesterday. Motorists crossing West Hawai'i had to use other routes.

The fire was still considered a "runaway" brushfire last night, but Mamalahoa Highway reopened shortly before 5:30 p.m. when firefighters decided it had been generally confined within an area northeast of Waikoloa Village bordered by two highways and some lava flows.

County fire crews remained there last night watching for flare-ups that could jump the highway and cause new problems.

Crews with bulldozers yesterday cut firebreaks, and fire officials used four helicopters to dump water on the fire near the intersection of Mamalahoa Highway and Waikoloa Road.

There were no homes threatened by the fire and no injuries, but the fire was the largest since another South Kohala blaze started on Aug. 1, 2005, and raced through nearly 25,000 acres, forcing evacuations from Waikoloa Village.

Fire Chief Daryl Oliveira said yesterday's fire was suspicious for several reasons. The fire started at about 8:16 a.m. Sunday near the 7-mile marker of Waikoloa Road, which is one to two miles north of Waikoloa Village.

SUSPICIOUS SIGHTINGS

Oliveira said the fire started near an access road that served a cinder quarrying operation, and a witness reported seeing a red pickup truck speeding up from the scene as the witness approached the area of the fire.

Oliveira said there have been reports of a similar vehicle in the general area of other brushfires over the past month that were believed to be suspicious.

"We're working with police closely to try and identify any evidence, and to try and capture all the information from witnesses to try and focus their investigating," Oliveira said.

The fire burned 300 to 400 acres Sunday but spread rapidly this morning as offshore winds whipped the flames through pasture land overgrown with fountain grass and other dried non-native vegetation.

Strong winds initially pushed the fire south, but "during the night as the wind shifted around, that fire moved in different directions," he said.

A LONG, HOT WEEKEND

The blaze forced the closure of Mamalahoa Highway at 7:30 a.m. yesterday, cutting the main commuter road between Waimea and Kailua, Kona. Mamalahoa was closed from Kaiminani Drive to Waikoloa Road.

The winds also prompted temporary closures of Waikoloa Road, he said.

"This fire has little pockets of fuel, and we're fighting the areas that are most critical, and then a little section will flare up and move close to the road and we'll send a unit down to fight that, and maybe close the road temporarily while they work alongside the roadway," said county Civil Defense Administrator Troy Kindred.

Crews from the National Park Service, the state Department of Land and Natural Resources, the Pohakuloa Training Area and the county Department of Public Works joined county firefighters in the effort to suppress the blaze.

Two private helicopters joined a Fire Department helicopter and a CH-47 from the Hawai'i Army National Guard.

Oliveira said crews are using old utility roads and old firebreaks that fire crews were trying to use to contain the fire.

By dusk, Deputy Fire Chief Glen Honda said the effort had gone well, helped along by light winds and overcast skies.

"It has simmered down quite a bit," he said last night.

Kindred predicted there will be more helicopter water drops today to quench the fire, and Honda said firefighters plan to continue to construct firebreaks to seal off the fire from the dry pasture land around it.

The fire caps a long weekend for firefighters, who worked to contain blazes in the Waikoloa area, at Mahukona and at Puako.

The first was on Friday afternoon, when firefighters quickly suppressed a fire along Waikoloa Road.

At about midnight Friday another fire started along Akone Pule Highway and burned toward the Mahukona camping pavilion, forcing authorities to evacuate about 16 campers, Kindred said.

That fire burned about 200 acres, and firefighters planned to remain on the scene last night to make sure the fire didn't flare again.

The "extremely dry conditions" continue to worry firefighters, Kindred said. "It's dry as a bone."

INFORMATION SOUGHT

Kindred said he expected a fire command post will be maintained at civil defense headquarters through the Fourth of July holiday, and said equipment was prepositioned around the island to be ready for any new fires.

Big Island police are asking for the public's help in identifying anyone responsible for setting fires in South Kohala.

Police ask that anyone who sees suspicious activity or notices people along highways in the area who have no apparent car trouble or legitimate reason for being parked call the police central dispatch number immediately at 935-3311.

Anyone with information about any of the fires is asked to call Officer William Vickery of the South Kohala District at 887-3080.

Reach Kevin Dayton at kdayton@honoluluadvertiser.com.