(CNN) -- Red-flag warnings, indicating critical fire ignition conditions, were in effect Saturday in eastern Arizona, where a massive wildfire grew to 430,000 acres.
Still, crews were making progress in the eastern section of the Wallow fire, said Rita Baysinger, spokeswoman for the Southwest Interagency Incident Management team. Other firefighters were awaiting improved conditions.
Firefighters have created "lines" to contain the fire. To keep the fire from spreading, they burned off areas to destroy ground fuel that feeds the large fire. That work continued Saturday.
"Today is the day that the good work we did over the last two days gets challenged," U.S. Forest Service spokeswoman Suzanne Florey told CNN earlier in the day.
As of Saturday afternoon, the fire was 5% contained.
New Mexico health and environment officials said air quality for much of New Mexico and eastern Arizona was expected to worsen over the weekend because of wildfires.
Heavy smoke could affect those in sensitive groups, including children, pregnant woman, asthma sufferers and people with lung and heart disease, the New Mexico Environment Department said.
The National Weather Service said smoke plumes from Arizona wildfires will continue moving toward Santa Fe and Albuquerque.
Heavy smoke has permeated communities around the largest Arizona blaze.
"We have not seen the sun clearly for several days," Baysinger said.
The flames have consumed 29 homes, 22 of them in the evacuated city of Greer.
On Friday, air and ground crews concentrated on protecting residences and structures in and near the evacuated cities of Springerville and Eagar.
Power companies said Friday that they are still watching the huge fire and its potential impact on crucial transmission lines that supply power to hundreds of thousands.
The blaze -- about the size of Houston -- has caused authorities to evacuate thousands of people since the wildfire began sweeping through the Apache National Forest on May 29.
CNN's Phil Gast and journalist Craig Johnson contributed to this report.