A suspected arson wildfire raging about five miles northwest of downtown Thursday threatened homes, a school and a shopping center. Firefighters awaited the dawn to launch a "massive assault" on the ground and from the air.

Several helicopters were readied to drop water on the blaze along the banks of the Rio Grande (search) that started Wednesday night and had already consumed some 700 acres. Such air support missions are considered too risky in darkness.

"Right now we're all waiting for the morning and praying that it comes faster," Gov. Bill Richardson said. "It will be a massive assault."

All of Albuquerque (search)'s firefighters were called into duty.

"As soon as the sun comes up we'll start sending them in," said Lt. Lynn Reule. About 125 Albuquerque firefighters were on the line just after midnight Thursday; another 100 from outside agencies were poised to relieve them.

Richardson also summoned various National Guard (search) all-terrain vehicles and helicopters and requested federal help. Several roads were also closed and traffic was choked in parts of the city.

Mayor Martin Chavez said evidence suggested the wind-driven blaze that broke out at about 8:30 p.m. was not merely a flare-up of a Tuesday fire that started about a mile to the south.

"It has more than one point of origin which is suggestive of arson," Chavez said.

No arrests were immediately made.

The fierce flames and resulting thick smoke were visible in many parts of Albuquerque, a sprawling city of about 450,000. Ash fell in some areas.

No injuries were reported and no structures were damaged. But hundreds of homes in an exclusive area and several other subdivisions and apartment complexes were evacuated.

"We have over 100 homes that are very severely compromised," Chavez said.

Between 200 and 250 people were evacuated from the homes Wednesday night, Chavez said. Police officers rode through neighborhoods early Thursday and announced that residents must evacuate after a shift in the wind breathed new life into the fire.

At least three evacuation centers were set up throughout the city. Some residents also were evacuating livestock to the New Mexico State Fairgrounds.

With the fire raging several hundred feet from her home, Jo Chestnut packed up family belongings and headed for a shelter while her husband stayed behind to evacuate their thoroughbred horse.

"It is very overwhelming; the thought that someone may have started this on purpose is just frightening that there is that kind of evil," she said.

Chavez said firefighters would be working strictly on structure protection and would not be fighting the fire within the area near the river -- the bosque -- which contains salt cedar, cottonwood trees and other vegetation.

The disadvantage Wednesday night was that the fire could not be fought from above. Water drops from helicopters were key in containing a fire that burned in the area Tuesday night.

Tuesday's fire -- which also burned about 700 acres in the bosque -- was apparently caused by fireworks, Chavez said. It flared north from the Interstate 40 bridge over the Rio Grande. A house under construction was destroyed and another home was damaged; no serious injuries were reported.

Meanwhile, crews in Tuscon, Ariz., were digging breaks on the crucial northern and southern fronts of a wildfire that destroyed about 345 buildings last week in a mountaintop vacation hamlet.

For the first time since flames first roared toward the Mount Lemmon community of Summerhaven, firefighters battled the Aspen fire Wednesday without heavy winds.

"Every day we have a good day, we get closer to being out of the woods," said Carrie Templin, a spokeswoman for he team battling the blaze.

Gusts upward of 40 mph hampered firefighters almost since the fire began June 17 northeast of Tucson. Gusts hitting 60 mph helped drive the flames through Summerhaven June 19.

The blaze has charred 30,200 acres, much of it pine forest, but is now 35 percent contained. The cause remained under investigation.