An eye-stinging haze of smoke spewing from a gigantic wildfire in eastern Arizona added a potentially serious public health threat to the conflagration on Saturday as firefighters moved to counter spot fires erupting across the state line in New Mexico.
The 640-square-mile (1,660-square-kilometer) blaze remained largely uncontained and firefighters worried that a predicted return of gusty southwesterly winds in the afternoon would cause it to grow even larger.
"We expect the winds to be testing a lot of our lines out there," fire spokeswoman Karen Takai said.
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.
Concern about hazardous levels of air pollution spread beyond northeastern Arizona.
Winds were expected to carry the plume across western and central New Mexico to the Albuquerque and Santa Fe metropolitan areas, the National Weather Service said. Dense smoke was predicted in a half-dozen small communities.
"The amount of particulate matter, smoke in the air, is a big issue," Takai said.
Concern was greatest for the elderly, young children and people with respiratory illnesses.
"Go visit your doctors, see what they say you should do," Takai advised the public.
Guarding the mountain town of Greer, firefighter Matt Howell, 28, described the difficulty of working in such 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, 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.
Lighter winds Thursday and Friday helped the 4,400 firefighters make progress, but critical fire conditions remain.
Fire crews plan to try to strengthen what lines they've been able to establish and continue burning out forested areas in front of the main fire to try to stop its advance. Containment was estimated at just 6 percent, on the northeastern edge.
The advances came on the fire's north side, near the working-class towns of Springerville and Eagar on the edge of the forest. Nearly 10,000 people have been evacuated from the two towns and from several mountain communities in the forest.
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.
The Chediski began as a signal fire and merged with the Rodeo, which was intentionally set by a firefighter who needed work. Together they burned 732 square miles (1,895 square kilometers) and destroyed 491 buildings.
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 (546 square kilometers) 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 late Friday and fire officials hope to have it fully contained by late June.