(CNN) -- A record wildfire raged on in southwestern New Mexico on Sunday, belching out a wall of smoke as it devoured thousands of acres and advanced across the rugged wilderness.
Authorities cautioned children, adults with heart disease and other sensitive groups to stay indoors as the growth potential for the blaze remains high.
The blaze -- the biggest in the state's history -- has scorched an area more than one and a half times bigger than Chicago.
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A total of 1,236 personnel are fighting the wildfire, which was 17% contained late Saturday, forest service officials said.
Two separate lightning strikes started two wildfires that merged, creating the giant fire.
Lightning ignited the Whitewater Baldy Complex wildfire last month, sparking a blaze that has devoured more than 227,000 acres in the southwest portion of the state.
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 away, according to Forest Service officials.
The two fires in the Gila National Forest merged May 23, enhanced by drought and sustained winds of 40 mph to 50 mph, authorities said.
Extreme drought could mean the smoke in the region will persist until the monsoon season, which typically begins in July, said Catherine Torres, secretary of the New Mexico department of health.
Authorities will allow residents back into the community of Mogollon on 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.
The blaze is 15 miles east of Glenwood, New Mexico.