New Mexico officials are warning residents of potentially hazardous air quality over the weekend from throat-burning smoke spewing from a gigantic wildfire in eastern Arizona that has been blazing for several weeks.

The 1,740-square-kilometer fire jumped the state line last Friday as firefighters moved to counter spot fires sprouting up in New Mexico and lighting their own fires to beat it back.

Health officials warned residents as far away as Albuquerque and Santa Fe about potential respiratory hazards, noting sensitive groups such as those with asthma, lung or heart disease, children, pregnant women and seniors should take extra precautions.

"Your eyes are your best tools to determine if it's safe to be outside," said Chris Minnick, a spokesman for the New Mexico Department of Health.

The forest fire remained largely uncontained and officials said the return of gusty southwesterly winds last Saturday stoked the blaze where it had been just smoldering before.

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

The situation yesterday could get even worse, said Mark Shaffer of the Arizona Department of Environmental Quality.

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."

New Mexico officials were monitoring air quality and are advising residents to pay close attention to conditions.

"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."