Updated

RATON, N.M. -- A wildfire burning along the New Mexico-Colorado border more than doubled in size in a matter of hours Monday as crews worked to protect evacuated homes and businesses, while the closure of about 20 miles of the main north-south highway through both states sent travelers hours out of their way.

Raton residents watched as trees on the hillsides just outside the northeastern New Mexico community burst into flames while smoke billowed into the air and air tankers passed overhead.

"It's very close. We're watching trees explode before our eyes. It's horrendous," said Barbara Riley, a schoolteacher and owner of the Heart's Desire Bed and Breakfast in Raton.

The Track fire had grown to 6,000 acres by Monday afternoon, less than a day after it was first reported. It destroyed seven structures, including outbuildings and hunting cabins, and damaged Raton's watershed before crossing into Colorado by evening. At nightfall, officials were reporting zero containment.

The blaze started Sunday on the west side of Interstate 25 and jumped to the east side that afternoon. It moved north toward the New Mexico-Colorado state line, and also to the east and southeast toward Raton, Sugarite State Park and Bartlett Mesa.

Between 800 and 1,000 people have been out of their homes northeast of Raton since Sunday night. Some were staying at a shelter that had been set up for evacuees at Raton's convention center.

I-25 between Raton and Trinidad, Colo., remained closed Monday because of the fire, and law enforcement officers were trying to ease the backup that the road closure caused by rerouting traffic.

Of the plume of smoke rising from the hills, Raton Mayor Neil Segotta said: "It looks like your worst nightmare."

In addition to homes and businesses threatened by the flames, Segotta said other concerns included the city's water treatment plant and the watershed. Raton depends on the watershed to feed a series of lakes that it uses for drinking water supplies.

State forestry spokesman Dan Ware said the fire picked up considerably Monday. Its quick spread was fueled by strong winds, dense vegetation and dry conditions.

Air tankers and a Blackhawk helicopter from the New Mexico National Guard were used throughout the day to slow the fire and cool areas where ground crews were building fire lines and providing structure protection in the small subdivisions on the outskirts of town.

The fire was burning mostly pinon and juniper in rugged terrain. The flames were most active west and north of Raton, Ware said.

Segotta said there was chance the evacuation order could be expanded depending on the wind direction.

"This fire to the west, we're keeping an eye on it. If the wind should change and shift the fire into a southerly direction, it could very easily encircle Raton from the west side," he said.

The Federal Emergency Management Agency has approved a grant to help New Mexico pay for up to 75 percent of the cost of fighting the fire.

Gov. Susana Martinez planned to visit the Raton area on Tuesday to be briefed on the firefighting effort and to meet with residents affected by the blaze.

New Mexico officials pointed to the Track fire and the northeast edge of the Wallow fire burning along the New Mexico-Arizona border as a warning for residents of the fire danger across the state. Persistent dry and windy conditions have resulted in hundreds of thousands of acres being charred in the state so far this year. Most of the state is suffering from severe to extreme drought conditions.

Firefighters in northeastern New Mexico shouldn't expect much help from Mother Nature, said Maria Torres, a meteorologist with the National Weather Service in Albuquerque. The forecast through the weekend calls for low humidity, little chance for rain, brisk winds and above normal temperatures.

"We have critical fire weather conditions," she said.

In southeastern New Mexico, firefighters were battling a 1,500-acre blaze near Carlsbad Caverns National Park. The park was closed Monday, and officials said it would reopen when conditions are safe.