The Taylor Bridge fire, which has burned more than 28,000 acres, is 10 percent contained, incident commander Rex Reed said Tuesday evening.
Reed said that containment line was built around the southeast corner of the fire.
The fire continues to spread destruction through Kittitas County, destroying dozens of homes and forcing hundreds of people to move to safer ground.
The fire covers more than 28,000 acres. Flames have destroyed 60 homes, and many other outbuildings and structures remain threatened.
The Department of Natural Resources pinpoints the start of the fire at Taylor Bridge, where a construction crew sent the first spark.
So far, no injuries have been reported but hundreds of people have been evacuated. The fire came to within six miles of Ellensburg
A state of emergency was declared Tuesday for Kittitas and Yakima counties as firefighters from multiple jurisdictions fought to contain the fire.
"DNR notified us today that access to Washington National Guard helicopters would assist in their efforts and this proclamation makes available those resources,” said Gov. Chris Gregoire.
The Washington National Guard deployed two helicopters equipped with water buckets on Tuesday afternoon.
More than 800 firefighters are expected to be on the scene by Wednesday.
The rush is also on to save horses and livestock, which for many residents is their livelihood. Hundreds of animals are being housed at the Kittitas County Fairgrounds.
Power is out to about 400 homes near Cle Elum and some people may be without power for up to a week.
The fire started Monday afternoon and grew from 2,800 acres to more than 20,000 in a matter of hours. By Tuesday afternoon, the fire had grown to more than 28,000 acres.
Among the hundreds of firefighters on fire lines Tuesday are 140 inmates from the Washington Department of Corrections, ordered there by Governor Chris Gregoire.
Wind whipped the flames overnight, and KING 5 Meteorologist Jeff Renner said there won't be much improvement in the weather, with temperatures heating up and the winds shifting from west to east.
Houses from Cle Elum to Thorp have been evacuated. As winds shifted toward pockets of subdivisions between Interstate 90 and Highway 97, people in about 450 homes awoke in the middle of the night to firefighters at their doorstep.
One firefighter said he had never seen a fire move so quickly. As a result of a rain in June followed by drier conditions in July, the east slopes of the Cascades are filled with combustible tinder allowing the fire to burn hot and quick.
The Federal Emergency Management Agency (FEMA) authorized the use of federal money to fight the flames. It's also the top priority of the Department of Natural Resources, as well as the Washington State Patrol and the Emergency Management Department.
Central Washington University will help by housing dozens of evacuees and firefighters. Some residents still in their homes have also opened their doors to state crews.
A state incident management team is in charge of crews and fire operations and local fire districts continue to work with the state. Fire information line: 509-649-0039. Updates and details online: inciweb.org.
Two community meetings are scheduled for Wednesday where area residents can learn more about the fire response and recovery. The meetings are scheduled for 4 p.m. at Cle Elum-Roslyn High School gymnasium, and 7 p.m. at Central Washington University's Student Union and Recreation Center.
The Kittitas Community Connect Facebook page has helped many evacuees stay in contact with one another.
KING 5's Gary Chittim and Susan Wyatt contributed to this report.