A fast-moving wildfire forced the voluntary evacuation of a ranching community Sunday as flames roared through tinder-dry fuel in southern Colorado (search).

The 8,000-acre blaze — which quadrupled in size in 24 hours — was threatening 750 houses, outbuildings and other structures in the Beulah Valley (search), about 150 miles south of Denver.

It was unclear how many people decided to leave. Cars and trucks packed with clothes, food and personal belongings were parked along a stretch of rural highway as evacuated residents watched black smoke rise from the hillside.

"Three years ago during the drought, I pretty much made peace with the fact that we could lose it all," said Dave Van Manen, referring to devastating wildfires that engulfed parts of Colorado in 2002.

Spending his 29th wedding anniversary standing on the asphalt of Colorado 78, his car stuffed with business files and other items, Van Manen said he was fully aware he could lose his house and office.

The fire had already forced the evacuation of 150 homes in surrounding areas. It generated so much smoke at one point that aircraft weren't able to get close enough to drop retardant on its center.

Elsewhere, fire crews in South Dakota got help Sunday from a tanker airplane as they battled a 3,500-acre blaze that had destroyed two homes in the Piedmont area of the Black Hills, northwest of Rapid City (search).

Evacuation orders remained in effect in and around the Piedmont on Sunday for those told to leave their homes Saturday night. Firefighters had no estimate of how many people have been evacuated.

Lightning was suspected as the cause of both the Colorado and South Dakota blazes.

Thirteen large wildfires were active Sunday in nine states and had burned more than 688,000 acres, according to the National Interagency Fire Center. Since January, wildfires have burned slightly more than 3 million acres, similar to the acreage burned by the same date last year.