WINDSOR, Colo. – Tornadoes touched down in northern Colorado and southern Wyoming on Thursday, damaging buildings, flipping vehicles and killing at least one person.

The National Weather Service said a large tornado touched down just after noon near Platteville, about 50 miles north of Denver. It then moved northward through or near several towns, tearing the roofs off buildings, downing power lines and crumpling farm equipment.

A second tornado touched down later in near Johnstown, about 10 miles northwest of Platteville, the weather service reported. There were no immediate reports of injuries.

Windsor, a farm town of about 16,000, appeared the hardest hit. Video footage showed a dark gray funnel perhaps a quarter-mile wide near the town with heavy hail and rain. At least one residential neighborhood in Windsor appeared to have suffered heavy damage. Television footage showed several rail tanker cars lying on their sides in downtown Windsor.

“It passed right over us like a big, white monster,” said 87-year-old Windsor resident Thomas Coupe.

Weld County Sheriff John Cooke said a man was killed at a campground west of Greeley. He declined to say how the man was killed.

Emergency personnel were still trying to determine how many people were hurt, and how badly.

At least seven people were taken to the Medical Center of the Rockies in Loveland with injuries, said hospital spokesman Gary Kimsey. The nature and extent of their injuries were not immediately known.

“We have every type of injury, broken bones, cuts, bruises, from everything from falling trees to broken glass hitting them,” said Jolene Schneider, spokeswoman for the Windsor Fire Department. “Only thing we are trying to figure out now is how many and how severe.”

Splintered wood, mangled metal and other debris cluttered roads, yards and agricultural fields in and around Windsor.About 130 children at a daycare center in the town were reported safe after the storm passed through; playground equipment outside the center was damaged.

“My house is gone,” said Pete Ambrose, a caretaker at a Weld County campground outside Greeley. “I lost my dog. I lost my cats. I lost my camper. I lost everything.”

Windsor resident Liz Meyer, 65, said she heard thunder and hail and rushed with her dog into her basement. Her house wasn’t damaged, but a 60-foot tree was uprooted from two blocks away and dumped near her home. “And look. It went into the street instead of into my house,” Meyer said.

Police officers were going door to door through Windsor looking for survivors, said Greeley police Sgt. Joe Tymkowych. “We’re hoping to finish that by nightfall,” Tymkowych said.

Tymkowych said he was about a half-mile from the tornado as it swept through the western edge of Evans and Greeley, an area that is mostly corn fields.

“It was a tornado that just sat on the ground,” Tymkowych said. “The amount of swirling debris and dust was just amazing, about a block, a block and a half wide. You could see debris just rotating, light poles, trees, you could see items being cast out from the sides, the edges of the tornado.”

Gov. Bill Ritter declared a state of emergency for Weld County, mobilizing the Colorado National Guard to assist with disaster response. Ritter and officials from the Federal Emergency Management Agency planned to tour the area by helicopter Thursday night.

All of northeastern Colorado was under a tornado watch through Thursday night, the National Weather Service said.

Interstate 25, the state’s main north-south highway, was closed for several hours after the storm before being reopened. Parts of state Highway 85, an alternate route, remained closed. Schools that had been locked down because of the storm reopened about an hour after it passed.

Some 60,000 customers lost power in the area, but power was later restored to all but 15,000 of them, according to XCel energy.

A tornado warning also was issued for an area about 100 miles northeast of Denver, but there were no reported tornadoes. KUSA television reported a funnel cloud was spotted near Longmont, about 30 miles north of Denver, but there were no immediate reports of damage.

Meanwhile, National Weather Service meteorologist John Griffith said a tornado touched down in Laramie, Wyoming, on Thursday afternoon.

Griffith, who works in the agency’s Cheyenne, Wyo., office, said he had received reports that the storm had damaged a two schools and a Wal-Mart.

Phone calls made to the Albany County School District and the local schools were not answered.

“With all the activity going on right now, it’s hard to get confirmation because there’s a lot of excitement going on to say the least,” Griffith said. “But I’m confident in saying there was a touchdown.”

State troopers responded to reports of vehicles turned over on Interstate 80 in Laramie, a dispatcher with the Wyoming Highway Patrol said.

On its Web site, the Wyoming Department of Transportation Web posted video showing a tractor trailer on its side and a boat that apparently had been blown off of a flatbed trailer on the interstate.

The weather service issued a tornado warning for western Laramie County just before 3:30 p.m. The warning stated that law enforcement reported spotting a tornado 10 miles southeast of Cheyenne, moving northwest at 53 mph.

The department of transportation said several southeast Wyoming roads, including I-80 was between Cheyenne and Laramie, were closed because of severe weather.

Associated Press writer Matt Joyce contributed to this report