CHILOQUIN, Ore. (CBS SF/AP) — A massive pyrocumulus cloud towering over the Bootleg Fire sent an avalanche of hot embers and gusty winds raining down on the fire line, helping the blaze grow to 241,407 acres with just 7 percent containment early Friday morning.

Pyrocumulus clouds are created by a wildfire’s intense heat and smoke. The fire creates its own weather system that spreads the flames. The greatest fear is that the towering column of smoke and embers will collapse, sending strong down drafts that will accelerate the spread of the blaze.

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That’s what happened Thursday.

“We had quite a column build (over the fire),” said fire spokesman Kyle Gibbons in his Friday morning Facebook update. “That column collapsed sending embers and fire across our primary containment line. So we picked up a couple of slop overs last night.”

Firefighters were all pulled back to safe areas late Thursday due to the intense fire behavior and were scouting ahead of the main blaze for areas where they could make a stand by carving out fire lines to stop the inferno’s advance.

“The Bootleg Fire perimeter is more than 200 miles long- that’s an enormous amount of line to build and hold.” said Rob Allen, Incident Commander for the Pacific Northwest Area Incident Management Team 2.

Gibbons said the fire was advancing as much as 3 miles a day eastward. Officials said they were now fearful the massive blaze would merge with the much smaller Logg Fire.

Authorities ordered a new round of evacuations Thursday amid worries the fire, which has already destroyed 21 homes, will continue its advance toward Summer Lake.

An initial review Friday showed the fire has destroyed 67 homes and 117 outbuildings overnight in one county. Authorities were still counting the losses in a second county where the flames are surging up to 4 miles a day.

The blaze has forced 2,000 people to evacuate and is threatening 5,000 buildings that include homes and smaller structures in a rural area just north of the California border, fire spokeswoman Holly Krake said.

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Burning tinder-dry brush and timber, the Bootleg Fire has stymied firefighters for nearly a week with erratic winds and extremely dangerous fire behavior.

“Extreme, crowning, running, spotting,” federal fire officials said of the conditions in a Friday morning update. “Fire remains very active with significant acreage increases due to hot, dry, and breezy conditions, and plume-dominated fire behavior. Poor humidity recovery at night is contributing to active fire spread through the night time period. Robust spread rates are being generated by drought-affected fuels. Expecting similar conditions for the next several days.”

The northeastern march of the fire also continues to threaten Path 66 — an electrical line corridor linking the California grid with power generators in the Northwest.

“Power supplies to the California ISO service territory, which covers about 80 percent of the state, have been reduced by as much as 3,500 megawatts because of the fire,” California power grid officials said earlier in the week.

On Thursday, Gov. Gavin Newsom ordered additional California resources to head to Oregon and join the nearly 2,000 firefighters on the lines.

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Two strike teams consisting of Type 3 and Type 6 engines from Fremont, Oakland, Hayward, Alameda County, South San Francisco, San Bruno, the Central Fire District, San Mateo and Kentfield had been dispatched earlier in the week.