More wildfire fighters needed in Colorado

The Hayman fire continued to burn out of control Tuesday.

DENVER, Colorado (CNN) -- Officials issued a plea Tuesday for 800 more firefighters to join those battling what has been called the largest wildfire in Colorado history, which had burned nearly 90,000 acres by nightfall.

The firefighters responding from across the country will join more than 500 who have been fighting the so-called Hayman fire since the weekend.

Fanned by northeasterly winds, the blaze consumed 10,000 acres Tuesday and threatened Denver's southern suburbs, said Joe Colwell, a spokesman for the interagency force fighting the fire.

Wednesday could bring similar conditions, he said late Tuesday.

"We have an extreme potential for growth," Colwell said. "It's hard to predict what this thing will do."

By day's end, the fire had destroyed 21 homes and 510 other structures since it began Saturday.

The fire, which sprung from an illegal campfire, had forced families to evacuate from 1,500 homes, and 2,500 more homes were threatened, Colwell said. He was not sure how many people had been evacuated.

Firefighters had contained about 5 percent of the blaze by day's end, Colwell said

'Not out of the woods'

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Earlier Tuesday, Colorado Gov. Bill Owens offered a grim assessment of the situation facing home and business owners near Denver.

"With the winds starting to pick up, with the heat building, with the humidity falling, the fire professionals have told us that this fire is still very, very dangerous," Owens said after getting an airborne view of the blaze.

"... We're not out of the woods, so to speak."

He spoke at a news conference along with Interior Secretary Gale Norton and Federal Emergency Management Agency Director Joe Allbaugh.

Behind Owens, beyond a tree-filled ridge, smoke rose from the "heel" of the fire. Officials said the fire had crossed a containment line at the southeast end of the burned area.

One positive development took place on the northeastern end of the fire, where the blaze moved into areas that were burned earlier this year in two fires -- one a controlled burn designed to reduce wildfire danger, said U.S. Forest Service official Rick Cables.

That has "has slowed the spread there, and we've got our fingers crossed," he said.

Fire officials also said the fire was spreading at about a half-mile per hour, approximately half of its peak speed.

Nevertheless, Allbaugh said, "This is a serious situation and everyone needs to understand the gravity that we're faced with now."

Residents leave

Some residents from the 700-home Roxborough Park subdivision and the 2,000-home Roxborough Village, both south of Denver, left their homes as a precaution as the fire edged closer, according to the constable for the Roxborough Park Metropolitan District. He said there was no mandatory evacuation order.

About 3,000 people previously were evacuated from other areas, Cables told CNN earlier Tuesday, and that number could reach 40,000 depending on the path of the fire.

"We've got 'trigger points' set up depending on what the weather does and what the fire behavior does," Cables said. "This fire is just really devastating."

"It's not very probable that it will reach Denver, but we are concerned the head of the fire near Roxborough State Park could grow in the direction of Denver, depending on the wind gusts today," said Ralph Swain of the Rocky Mountain Coordination Center.

Another major fire known as Coal Seam, in the Glenwood Springs area 160 miles west of Denver along Interstate 70, burned 10,000 acres.

Cooler temperatures had made firefighting conditions there more favorable Tuesday, Swain said. That fire wasn't growing significantly, Swain said.

There are at least seven other fires burning in Colorado. The one near Denver has spread a haze over the city. Many residents on Denver's south side said ash was falling on their homes and cars.

A satellite photo showed smoke from the fire spreading north into Wyoming, Nebraska and even the Dakotas.

The Coal Seam fire has overlapped the path of the 1994 Storm King fire, where 14 firefighters were killed when the winds changed the direction of the fire, trapping the men in the blaze.

One official said that was why firefighters were not deploying in front of the current blazes.

Colorado is a tinderbox with the fire threat in half the state rated in the extreme category, with the rest of Rocky Mountain state earning a high to very high fire danger rating from the U.S. Forest Service.

At the Tuesday afternoon news conference, Norton spoke of the fire danger throughout the West brought by severe drought.

"This a year when severe drought is affecting much of the Rocky Mountain area, and especially the southern part of the Rockies," the Colorado native said. "All across this area we are seeing record low amounts of rainfall and snow pack."

-- CNN Reporter Lilian Kim, Newsource Producer Kristin Fraser and CNN.com Content Editor Mark Davis contributed to this report.