DENVER - Government offices and schools were closed and mail delivery suspended for a second day Thursday after a powerful blizzard dumped more than 2 feet of snow along Colorado's most populous region and stranded travelers.

Traffic along southbound Interstate 25 toward Denver at the Colorado Highway 7 overpass comes to a standstill during a winter storm, Wednesday, Dec. 20, 2006, near Erie, Colo. [AP]

Denver, Colorado Springs and other cities along the Rocky Mountain Front Range were virtually ghost towns, with cars and SUVs slipping, sliding and crawling through thick snow toward the suburbs Wednesday.

Some 4,700 people hunkered down overnight at Denver International Airport, where flights in and out were canceled, spokesman Steve Snyder said.

"It feels like I'm a refugee," said Lisa Maurer, a graduate student at the University of Wyoming who was stuck at the airport while on her way home to Germany.

Bus and light rail service in a six-county region was suspended. The State Patrol reported a rash of collisions, some involving several vehicles, but no fatalities.

More than 30 inches of snow fell in the mountains and up to 2 feet fell in the Denver metro area, with snow expected to let up by noon Thursday. Winds cut visibility and whipped up drifts several feet high on the plains.

Gov. Bill Owens declared a state of emergency and activated the National Guard, which assisted dozens of motorists on the highways around Denver and delivered diapers, formula and bottled water to the airport.

Long stretches of Interstates 70 and 25, the main east-west and north-south routes through the Mountain West, were closed. Interstate 76 was closed from Denver to Nebraska.

"They pulled everyone off the highway," said Leon Medina, manager of a truck stop on Interstate 25 in Walsenburg, about 130 miles south of Denver. "Cars are all around the building. Trucks are all over, trucks and cars pulled into ditches."

At least 270 people took refuge at seven American Red Cross shelters in the metro area, though that number was expected to rise as motorists arrived by the busload early Thursday, said Robert Thompson, spokesman for the Mile High chapter.

"It's just amazing how many people are still out there," Thompson said.

Shelters also were open in Fort Collins and Colorado Springs, and the Red Cross provided 140 cots for nearly 350 people stranded at a Greyhound bus station in downtown Denver, Thompson said.

Weather Service program manager Byron Louis said it was the most powerful storm to hit Colorado since March 2003, when a massive blizzard dumped up to 11 feet of snow and was blamed for at least six deaths.

Major malls closed early Wednesday, and one, Flatirons Crossing Mall in Broomfield, northwest of Denver, offered warmth for motorists stranded along U.S. 36, the major link between Denver and Boulder.

Mail service was canceled in the eastern half of the state because roads were impassable for mail carriers getting to work and for trucks delivering mail four days before Christmas.

"We don't want to take the risk of clogging up the system just by being out there," said Al DeSarro, a U.S. Postal Service spokesman in Denver. "We're considering delivering on Sunday to make up for what's sure to be a backlog of mail."

Denver International Airport was closed to all flights at mid-afternoon Wednesday, and more than 1,000 flights were canceled through Thursday. No time was set for runways to reopen.

United Airlines canceled more than 670 flights into Denver and 160 that had been scheduled to take off before noon on Thursday. Frontier Airlines canceled up to 190 flights.

"I'm just happy to be alive. It was a terrifying drive," Sara Kelton said of her two-hour slog over slick, snow-clogged roads to get to the airport.

Thirteen hours after he left his Denver office for a bus ride home to Boulder, Alan Barr was stuck at a Red Cross shelter in Denver, barely closer to home than when he left for work.

He trudged into the shelter at about 12:25 a.m. Thursday with other discouraged riders faced with the prospect of spending the night in a college gymnasium.

"Days like today are an exception," he said. "I believe in public transportation."

Fellow rider Matt Notter of Boulder summed it up:

"It was comical for a while," he said. "Then we realized, this is an all-night thing."