DALLAS (AP) _ Grass fires that already consumed thousands of acres of parched land in Texas, Kansas and Oklahoma kept popping up Saturday, needing only a spark from a passing train or an errantly tossed cigarette butt to ignite them.

Grass, trees and shrubs, crackling dry from lack of moisture, are consumed in seconds by the flames. The ensuing fires are pushed by gusty winds and roar along at speeds of 40 mph or more across vast stretches of open prairie.

``I've never seen them this fast,'' said firefighter Pat Harbold, who spent much of this past week battling a 16,500-acre fire near Poolville, Texas.

``You get out of the way or they'll run right over. You just try to contain them. It's something out here on this prairie ... you'll have flames taller than your truck and embers flying up in front of you. There's rabbits and other animals trying to get out of the way.''

Similar fires throughout Oklahoma destroyed 54 homes, injured at least 12 firefighters and left one fire chief dead of cardiac arrest near Okemah, about 70 miles east of Oklahoma City.

One of the largest fires charred tens of thousands of acres from Oklahoma's rural Woods County across the state line into Kansas, burning some barns and outbuildings in its path as it raced down canyons and across dry rangeland.

At least three fires had sprung back to life Saturday in Medicine Lodge, Kan., about 25 miles from the state line. ``It's nothing but miles and miles of grassland and ravines,'' said volunteer firefighter Richard Becker.

A grass fire in northeast Kansas forced the evacuation of about half the 900 residents of Auburn, a town near Topeka. Four homes and a fire truck were destroyed and two firefighters were injured.

The fire was about five miles long and three miles wide Saturday afternoon as it crept within a mile of the town.

The fire in Poolville, 35 miles west of Fort Worth, injured more than 50 people and destroyed more than 150 homes and other buildings.

Hundreds of fires continued to burn Saturday, including a 6,000-acre blaze in Stephens County, about 40 miles west of Poolville, and a 10,000-acre fire in Shackelford County in northwest Texas, and a 12,000-acre fire in Clay County. Those three fires were under control.

The grass fires _ some 3,000 separate blazes since January _ have consumed 158,000 acres, an area about three-quarters the size of Dallas.

Last year, 1,510 grass fires consumed about 18,500, said Jo Schweikhard Moss, of the State Division of Emergency Management.

Firefighters chase the flames in small, four-wheel drive ``bush trucks'' equipped with 500-gallon water tanks.

``You think you have it out and you look 100 yards past you and there's another one started,'' Harbold said. ``I've never seen them this fast.''

Fires that burned 15,000 acres of grassland near Fort Hood, about 50 miles southwest of Waco, were brought under control Friday night, said Sgt. Troy Rolan.

Roughly 1,200 soldiers, firefighters and civilian volunteers have been battling the fires, and helicopters dropped water.

President Clinton on Friday declared an emergency in 21 counties in north, central and east Texas, allowing federal equipment and crews to help out.

North Texas has received only about 7 inches of rain since August. The normal rainfall for that period is about 17 inches, said Lori Bovitz, a meteorologist for the National Weather Service. Prospects for rain are slight.

The drought was preceded by several years of abundant moisture, which allowed the dense prairie grass to thrive before drying up.

In Oklahoma, more than 250,000 acres have burned since Feb. 13, said Ben Frizzell, a spokesman for the state Department of Civil Emergency Management.

In the town of Bristow, where 17 homes and two dozen barns turned to ashes, Fire Chief Bob Grant believes several of the blazes were the result of arson. No one has been arrested.

Roughly 110,000 acres had been burned in the Woods County fire that began when an utility truck caught fire as crews worked on a pole.