KANSAS CITY, Missouri (AP) -- A weather-beaten pickup truck sits among debris left after a tornado tore through Colorado.
No injuries were immediately reported, but a tornado warning remained in effect for Garfield and Kingfisher as storms continued to move east.
The latest twisters hit even as workers were picking through debris after tornadoes rampaged in western and central Kansas and northern Oklahoma for a second night in a row.
The city of Protection, Kansas, took a direct hit from a tornado Friday, although the damage seemed mostly limited to downed trees and power lines. The worst destruction occurred at a manufacturing plant, a Comanche County sheriff's dispatcher said.
"Emergency responders are going door to door to see if anyone needs rescuing," said Sharon Watson, spokeswoman for the Kansas Adjutant General's Department.
A man was injured when his vehicle was blown across a highway in Gove County, where at least 12 homes were destroyed or suffered major damage, Watson said.
At least two houses elsewhere in Kansas were destroyed, and several mobile homes in Lane County were ripped apart, some with people in them. No injuries were reported, Watson said.
In northern Colorado, meanwhile, officials were thankful the tornado that damaged 596 homes in Windsor on Thursday hadn't caused more casualties. One man died -- at a campground outside neighboring Greeley. About 100 people were treated for broken bones, cuts, scrapes and bruises, and three were hospitalized for stress. Watch how day-care workers protected children »
The farm town of 16,000 has an automated system to call residents with alerts, but the storm developed so quickly that there wasn't time to activate it, public information officer Dan Hatlestad said.
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Windsor Mayor John Vazquez couldn't explain why there weren't more casualties.
"I don't have the answer for that," Vazquez said Friday. "The grace of God? It was a big storm."
The twister damaged or destroyed homes, businesses, dairies and farms in several Weld County towns Thursday. The storm system pelted the region with golf ball-size hail, swept vehicles off roads and tipped 15 rail cars off the tracks in Windsor, a farm town about 70 miles north of Denver.
Stormy weather, natural gas leaks and the threat of explosions kept hundreds of anxious residents from assessing the damage to their homes Friday.
Police and more than 100 National Guard troops cordoned off a particularly hard-hit area so utility crews could check each home for gas leaks, repair gas mains severed by uprooted trees, remove downed power lines and clear streets of shattered glass and debris.
It might take a day or more to secure the area, said Bill Easterling, commander of the emergency response team.
"I think at this point it's pretty much hit me," said a dejected Cindy Miller, a 46-year-old high school teacher. "I'm not going home for a while."
Before being ordered out Thursday, Miller found a wall to her house torn apart and insulation, glass, water and debris everywhere. Wood planks had penetrated a bathroom wall, and her trampoline was in a neighbor's yard.
Conditions converged in just the right way, time and place to produce "a pretty remarkable tornado," said Greg Carbin of the National Oceanic and Atmospheric Administration's Storm Prediction Center in Norman, Oklahoma.
A preliminary damage survey Friday by the National Weather Service showed the tornado that hit Greeley was likely an EF-3, with speeds from 136 to 165 mph, and the one that hit Windsor had wind speeds of 111 to 135 mph. Meteorologist Dan Leszcynski said it was unclear whether the twisters were one and the same.
Another tornado warning Friday forced workers to temporarily suspend cleanup and residents to scurry to shelter. At least two tornadoes were reported in the plains east of Windsor. No damage was reported.
The National Weather Service received reports that another tornado near the Nebraska line downed four power lines, snapped a fence and overturned a stock trailer.
In Oklahoma, an elephant trunk-shaped tornado was spotted about 10 miles northeast of Fort Supply on Friday. At least one home was damaged, but there were no reports of injuries.
On Thursday, a 14-year-old boy was killed when his stepfather drove onto a road in northwestern Oklahoma that had been washed away by heavy rain, authorities said Friday.
The city of Greensburg, Kansas, which was largely destroyed a year ago by a massive twister, suffered minor damage when a tornado hopped from the western edge to the eastern edge of town Friday.
"The funnel cloud went directly over the top of Greensburg," said Ray Stegman, Kiowa County emergency preparedness manager.
Small tornadoes were reported Friday in Platte County in Wyoming, said Chad Hahn, meteorologist with the National Weather Service there. Some damage was reported but no injuries.
About 100 people have died in U.S. twisters so far this year, the worst toll in a decade, according to the weather service.