SPRINGERVILLE, Ariz. - An eye-stinging, throat-burning haze of smoke spewing from a gigantic wildfire in eastern Arizona is beginning to stretch as far east as central New Mexico, prompting health officials to warn residents as far away as Albuquerque about potential respiratory hazards.

The 672-square-mile blaze was no longer just an Arizona problem on Saturday as firefighters moved to counter spot fires sprouting up across the state line and lighting their own fires to beat it back. The forest fire remained largely uncontained and officials worried that the return of gusty southwesterly winds during the afternoon could once again threaten small mountain communities that had been largely saved just a few days ago.

Levels of tiny, sooty particles from the smoke in eastern Arizona were nearly 20 times the federal health standard on Saturday. The good news was that was down from roughly 40 times higher a day earlier, but it was all at the mercy of the ever-changing winds.

Sunday could get even worse, said Mark Shaffer of the Arizona Department of Environmental Quality.

"Things got better but they're still bad," Shaffer said Saturday.

The microscopic particles, about 1/28th the width of a human hair, can get lodged in the lungs and cause serious health problems, both immediate and long-term, Shaffer said.

"Larger particles, you breathe in and you cough and it tends to get rid of it," he said, adding that the tiny particles get "very, very deep into your system and are very difficult to expel."

Shaffer said the forecast for today was "pretty scary."

"It's looking very unsettled, and they're predicting winds out of the southeast to the northeast and heavy impact along Interstate 40 ... It's very problematic for both states."

New Mexico officials were continuously monitoring air quality in their state and are advising residents from the Arizona border to Albuquerque to pay close attention to conditions.

"The people we're most concerned about are obviously those with chronic health conditions but when air quality gets this bad it can actually have negative effects on everybody," said Chris Minnick, a spokesman for the New Mexico Department of Health.

He said the state planned to issue an alert to residents Saturday to take precautions if the smoke gets worse, such as avoiding strenuous outdoor activities.

"Just because you can't see the fire doesn't mean there isn't an effect from the smoke blowing into the state," Minnick said.

Guarding the picturesque mountain town of Greer, where 22 homes and cabins were destroyed earlier in the week, firefighter Matt Howell, 28, described the difficulty of working in such smoky, choking conditions.

"You get in there and it's hard to breathe," he said. "You start coughing, can't get that good nice breath of air."

More than 30 homes have been destroyed since the fire began May 29, thousands of residents have fled communities and the blaze posed a potential danger to two major power lines that bring electricity from Arizona to West Texas, although officials said Saturday they had so far been able to protect the routes.

The fire began spotting across the state line Friday night and 150 additional firefighters and several fire engines were sent to bolster forces already waiting in New Mexico, officials said.

Lighter winds Thursday and Friday helped the 4,400 firefighters make progress, but critical fire conditions remain for the 4,400 firefighters working the blaze.

Containment regressed slightly to just 5 percent, on the northeastern edge.

In Greer, a smoky haze clung to fields, graying out the sky, and scattered plumes of smoke rose from the forest where spot fires persist.

"We expect the winds to be testing a lot of our lines out there," fire spokeswoman Karen Takai said.

Firefighter R.J. Carnright, 28, a local protecting his own town, reflected Saturday morning on the fight just days ago and looked ahead to what's to come.

"We put up a good fight and we're ready to do it again," he said, his face smeared with soot.

Nearly 10,000 people have been evacuated from the towns of Springerville and Eagar and from several other mountain communities in the forest, where officials said residents may be allowed back in soon, but also warned of lingering air pollution.

"Even when the word is given that you can come home, there's still going to be some air quality issues," said Eager Town Manager Bill Greenwood.

The fire is the second-largest in state history and could eclipse the 2002 Rodeo-Chediski fire in size, although only a fraction of the homes have burned. That blaze burned 732 square miles (1,895 sq. kilometers) and destroyed 491 buildings.

The current Wallow Fire in the Apache-Sitgreaves National Forest has destroyed 31 homes or cabins, fire spokesman Jim Whittington said. Two dozen outbuildings and a truck also were lost and five homes damaged in Greer when the fire moved in Wednesday night.

Firefighters are battling another major wildfire in far southeastern Arizona, also near the New Mexico line. The so-called Horseshoe Two blaze burned through 211 square miles or 135,000 acres of brush and timber since it started in early May. The fire has destroyed 23 structures but caused no serious injuries. It was 45 percent contained and fire officials hope to have it fully contained by late June.