(CNN) -- The largest wildfire in New Mexico's history continued to burn almost uncontrollably Saturday in the remote Gila Wilderness, belching enough smoke to prompt officials to caution that children, adults with heart disease and other sensitive groups should not go outdoors.
Since lightning ignited the Whitewater-Baldy Fire Complex wildfire on May 9, flames have devoured 227,000 acres -- more than 354 square miles -- in the southwest portion of the state. Even though 1,257 personnel have been fighting the conflagration, only 15% of it was contained Saturday, U.S. Forest Service officials said.
For purposes of comparison, the burn area of 354 square miles is more than one and a half times bigger than the city of Chicago's 227 square miles.
Two separate strikes of lightning caused the mountainous fire: the Baldy Fire started May 9 in an inaccessible area of the rugged wilderness, and the Whitewater Fire was reported on May 16 several miles west of the Baldy Fire, Forest Service officials said.
The two fires in the Gila National Forest combined May 23, enhanced by drought and sustained winds of 40 mph to 50 mph, authorities said.
It was the May 16 event that led crews to try to suppress the entirety of the fire but "the extreme fire activity, coupled with incredibly rugged terrain and large boulders falling down the steep canyons forced fire crews to pull out of the area after the first day of fighting the fire," the Forest Service said.
The fire began 15 miles east of Glenwood, New Mexico, and has been fueled by conifers, ponderosa pines, pinons, junipers and grass, Forest Service officials said.
Continuing growth potential for the history-making wildfire was "high" Saturday, the Forest Service said.
CNN affiliate KRQE reported that 12 seasonal homes in the Willow Creek area were destroyed.
Because of the state's current extreme drought, smoke in the region could persist until the monsoon season, which typically begins in early July, New Mexico Department of Health Secretary Dr. Catherine Torres said in a statement.
On Saturday, the Catron County Sheriff Department said it will allow evacuated residents back into the community of Mogollon, effective Monday, but an evacuation order for the summer cabins of Willow Creek remained in effect Saturday, according to the New Mexico Department of Homeland Security and Emergency Management.
"Because of the complexity of this fire, fire managers have brought in specialized resources," the Forest Service said in a statement. "One of those resources includes heli-rappellers. Heli-rappellers are one of the aerial resources brought in during early stages of a remote fire, especially where there is no good landing zone. The 'rappellers' will rappel from a helicopter into remote locations and extinguish fires or provide reconnaissance information."
Ten helicopters were deployed Saturday, authorities said.
The Gila Cliff Dwellings National Monument has been closed since Thursday, U.S. Forest Service Superintendent Steve Riley said earlier this week.