This is an archived article that was published on sltrib.com in 2016, and information in the article may be outdated. It is provided only for personal research purposes and may not be reprinted.

The Box Canyon Fire in the Uinta-Wasatch-Cache National Forest had grown to 4,000 acres by Sunday afternoon, and the Utah National Guard joined the effort to fight the blaze from the air.

The 97th Aviation Troop Command, 2nd Battalion, sent in two Black Hawk helicopters on Sunday, each with two pilots and a crew chief on board. The Black Hawks — which joined a third helicopter — were making repeated trips to nearby water sources to fill their 600-gallon buckets and drop the water on the flames, according to the National Guard.

The fire was 20 percent contained as of Sunday afternoon.

The National Guard said its helicopters are slated to continue assisting firefighting efforts on Monday.

The fire, first spotted on July 28 in Summit County about 12 miles east of Oakley and a few miles above the Smith and Morehouse Reservoir, was caused by an unattended campfire, according to the U.S. Forest Service.

The reservoir has been closed to all watercraft because it is being used as a water source for firefighting. Shoreline activities, such as fishing, are allowed but access is limited to a section of the shoreline.

The Ledgefork campground, Smith and Morehouse boat ramp, Smith and Morehouse trail, Mud Lake Flats and Erickson Basin also have been closed.

Smoke was visible throughout the Kamas Valley on Sunday and people with respiratory problems were urged to take necessary precautions.

For information on air quality, go to airnow.gov. Visit http://inciweb.nwcg.gov/state/46/ for more more information about the fire.

Twitter: @PamelaMansonSLC