Updated

Firefighters battling a Hawaii wildfire caused by young boys playing with a lighter are using helicopters and clearing terrain to attack the 1¼-square mile blaze.

The fire started in the Makakilo area of Oahu and has forced some 40 people in 20 homes to evacuate and damaged at least one residence, but no one has been hurt.

The parents of twin 7-year-old boys told investigators their sons inadvertently ignited the blaze with the lighter, Honolulu Fire Capt. David Jenkins said Saturday.

Since then, fire has chewed through about 800 acres of brush, grass and trees as strong winds pushed the flames uphill and into a rugged, inaccessible mountain area.

Jenkins said crews spent Saturday clearing a 30-foot wide swath around the threatened homes along Palehua Road as protection if the fire does approach.

He said fire activity was expected to be relatively calm overnight, but then pick up as the winds grow stronger Sunday.

So far the only damage has been a scorched wall and door of one home.

More than 100 firefighters, aided by water-dropping aircraft including four helicopters, were battling the flames.