Efforts to contain a vast blaze scorching the western US state of Oregon have failed, as forecasters said Friday that dry, unstable, and windy conditions were likely to keep fueling the massive wildfire.

The Bootleg Fire in southern Oregon, near the border with California, was just one among dozens of major fires raging across the drought-stricken western United States.

However, it grew overnight to 377 square miles (976 square kilometers) — greater than the size of New York City. The wildfire remains only seven percent contained.

"The Bootleg Fire perimeter is more than 200 miles long -- that's an enormous amount of line to build and hold," said firefighter commander Rob Allen.

"We are continuing to use every resource, from 'dozers to air tankers to engage where it's safe to do so especially with the hot, dry, windy conditions predicted to worsen into the weekend."

'Fire cloud' collapses

The inferno, which is growing by 4 miles a day, has forced 2,000 people to evacuate and is threatening 5,000 buildings, including homes and smaller structures in a rural area just north of the California border, fire spokeswoman Holly Krake said.

The fire is so large that it generates its own weather. "Fire clouds" are formed from superheated air rising to a height of up to 10 kilometers above the blaze, which can spawn lightning and high winds.

One such fire cloud collapsed Friday, spreading embers and forcing the firefighters to flee the fire lines.

"We're expecting those same exact conditions to continue and worsen into the weekend,'' Krake said of the fire-induced clouds.

Impact on neighboring California

The fire also threatened the power supply in California where heatwaves in the past years have put a strain on the state's grid.

California Governor Gavin Newsom announced that the state was sending reinforcements to Oregon even as the state battled its own fires, his office's emergency service said.

Demand for personnel and equipment across the Pacific Northwest has strained available resources. More than 1,900 firefighters and a dozen helicopters as well as airplane tankers and bulldozers were assigned to the Bootleg.

Caused by climate change

About 70 major active wildfires were listed on Thursday which has burned more than 1 million acres in 12 states, the National Interagency Fire Center in Boise, Idaho, reported.

The fire stands as the fifth largest on record in Oregon since 1900, according to state forestry figures.

Scientists have said the extremely dry conditions and heatwaves have been tied to climate change, making wildfires harder to fight.

Climate change has amplified droughts making the region warmer and dried in the past 30 years.

This has created the ideal condition for wildfires to spread out of control and inflict unprecedented damage, growing in both frequency and intensity.  

adi/rc (AFP, AP, Reuters)