More than 2,200 acres of land at the back of Nanakuli Valley have been burned since Tuesday, said Fire Department spokesman Capt. Emmit Kane. In addition, three fires that broke out Saturday night torched almost 600 acres in Wai'anae, including about 400 acres near several homes on Leihoku Street before firefighters contained them.

Firefighters worked until nightfall, then maintained fire watches through the night.

The fire yesterday burned into the state's Nanakuli Forest Reserve and near the edges of the The Nature Conservancy's Honouliuli Preserve, raising concerns about how much damage the fire would cause to native plants and animals.

Earl Pawn, a forester with the state Department of Land and Natural Resources, said about one-fifth of the Nanakuli Forest Reserve was burned as of 4:30 p.m. yesterday. It was not immediately clear yesterday afternoon if the fire had crept into the

"There are listed native plants in the area," Pawn said. "Three days ago it (the fire) was on the fringes (of the reserve), but now it's coming in from the north."

Pawn said it was too early to tell if any endangered species had been wiped out.

Pauline Sato, O'ahu program director for The Nature Conservancy, said Hawai'i forest fires are more damaging than those on the Mainland because the plants that repopulate scorched earth here are usually non-native species and more likely to burn again than the plants they replace.

"The Mainland forests have adapted to fire as a natural phenomenon," Sato said.

Fire yesterday ravaged Nanakuli Valley for a sixth day. The prolonged fire has frustrated residents, and the smoke has become a hazard for those with breathing problems. Andrew Shimabuku • The Honolulu Advertiser

Some firefighters lugged around 60-pound tanks of water to douse smoldering patches of scorched earth. Others carried shovels and chain saws to dig fire lines and to cut away brush. Tankers trucked water into the valley.

Four helicopters — two from the military, the Fire Department's Air One and a private helicopter on loan — supported the firefighters on the ground by making continuous water drops in the valley.

More than 25 federal firefighters worked yesterday afternoon to stamp out hot spots amid the more than 400 acres of burned brush near Leihoku Street.

About 1 p.m. yesterday at the top of the back bowl of Nanakuli Valley, a line of fire erupted and raced up the mountain toward the ridge line. Flames leaped from tree to tree, resembling a row of birthday candles igniting one after another.

Residents in the area expressed frustration about the smoke blowing through the valley.

"I get worried, my grandkids get asthma and my in-laws get asthma," said Dolly Naeole, a developmental therapist who has lived near the corner of Nanakuli Avenue and Haleakala Avenue for almost 40 years. "When I grew up, we never had fires like this."

Margaret Copp, a store manager who has lived on Haleakala Avenue for more than 20 years, said the smoke and flames Saturday night forced her to move her 3-month-old grandson to another house so he could breathe more easily.

"We've all been pulling out the insurance policies making sure they're current," she said, watering down her front yard as white plumes of smoke rose from the brush several hundred yards behind her home. "It's been a war zone for a couple of days and I feel so sorry for the firefighters."