Utah Army Guard Gen. Brian Tarbet said Monday he was "deeply sorry" about what he called a "systematic failure" at Camp Williams, about 30 miles south of Salt Lake City.
The commander accepted responsibility for the wildfire sparked Sunday that destroyed three houses, damaged a fourth and forced the evacuation of more than 1,600 homes. Officials said Tuesday that 450 homes remained evacuated.
Tarbet said no one checked to see that the National Weather Service had posted a "red flag" high-wind warning before the machine gun exercise was permitted to continue in tinder-dry conditions in the foothills of the Oquirrh mountains. He also said guard commanders waited two hours to call outside fire agencies for help.
Guard Lt. Col. Hank McIntire told reporters Tuesday that those responsible would be held accountable.
"If we need to take internal action, we certainly will," he said.
The Unified Police Department, an agency overseeing Salt Lake County, is enforcing an evacuation order for parts of Herriman, a community of about 18,000 residents at the southwest corner of the Salt Lake valley.
"We understand the frustration and how inconvenient it is to be forced from your home," police Lt. Don Hutson said.
With high winds predicted Tuesday afternoon, seven bulldozers, five aerial tanker aircraft and four National Guard Black Hawk helicopters were supporting more than 500 firefighters and guardsmen cutting fire lines.
It is the latest example of military training activities sparking large fires at Camp Williams and other facilities. Camp Williams, founded in 1926, covers 44 square miles, or nearly twice the size of Manhattan.
Utah National Guard officials said they can usually contain any flames, but local leaders questioned the decision to fire weapons at all.
"It's a regular occurrence with any type of training — small flare-ups we deal with," McIntire said Monday.
The flames were ignited about 12:40 p.m. Sunday by practice rounds from a .50-caliber machine gun. Officials said a fire crew with a fire truck thought they contained the fire until winds whipped up about 1:30 p.m. Unified fire officials were called at 3:22 p.m.
"Our fire crews were on standby, responded and corralled the fire. They got it under control, but the winds came up, and the fire spread and got beyond what we could handle ourselves," McIntire said.
Overnight winds of more than 40 mph fanned the fire across more than 6 square miles.
When the drill got under way, the National Guard said the fire hazard was moderate. There was little wind, temperatures were below 75 degrees and humidity was 13 percent, typical for Utah's dry climate.
Fires caused by artillery shells or other weapons at military installations are not uncommon. In May 2007, a flare dropped from an F-16 on a training flight sparked a fire that burned 17,000 acres in New Jersey. Artillery practice sparked a huge wildfire in July 2009 outside Marseille, France.
At Camp Williams, a fire touched off by artillery burned 500 acres in September 2006 and forced the evacuation of about 50 homes. None were destroyed. A more recent fire burned 300 acres in July.
Residents and Salt Lake County Mayor Peter Corroon questioned the National Guard's decision to hold live-fire exercises in dry conditions.
Hutson called the practice flare-up a "perfect storm" that kicked up violently with winds of 40 mph to 50 mph.
The fire has caused no major injuries, officials said, although two police officers were treated for smoke inhalation and a third for minor injuries after being hit by the vehicle of a driver trying to return home.
As smoke filled the sky Sunday, Dustin Spangler and his neighbors saw no reason to wait any longer for help.
They organized a volunteer brigade to prepare for "the fire coming over the hill." The actions may have saved Spangler's home, which suffered only smoke damage.
Associated Press researcher Monika Mathur in New York City contributed to this report.
(This version CORRECTS spelling of Camp Williams.)
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