The helicopter was one of seven working a fire in central Utah caused by lightning on July 27.
The Federal Aviation Administration (FAA) confirmed the helicopter crashed in Richfield, about 258km south of Salt Lake City.
Conditions were good enough for aircraft to fly when the helicopter crashed, Tyler Hecht from the Great Basin Incident Management Team said.
The Sikorsky S-64 helicopter, which had been working in an area with steep terrain, ignited another fire when it crashed.
Hecht told reporters he did not know how long the helicopter was flying before it crashed.
Response teams had not been able to access the scene of the accident by Friday evening due to the flames, but hoped to do so in the next 24 hours, officials said.
"We didn't want to put them at bigger risk," Sevier County Sheriff Nathan Curtis said.
"We'll get them in there as soon as we can."
It was unknown if fire had overrun the crash scene, Hecht said.
Firefighting efforts were paused after the accident but later resumed.
The National Transportation Safety Board and FAA will investigate, but might not be able to safely reach the scene immediately if the wildfire is burning nearby.
Sikorsky S-64 "Skycrane" helicopters are used commercially and by government agencies for firefighting and other purposes.
They can be equipped with tanks to drop water or fire retardant onto blazes.
Fire crews were warned on Friday morning there would be erratic winds, dry fuels and hot temperatures and the potential for dry thunderstorms and lightning.
Red flag warnings were in effect.
The fire in the Fishlake National Forest near the small community of Kanosh, Utah, had grown to 427 square kilometres and was 19 per cent contained by Friday morning.
More than 600 firefighting personnel are battling the blaze, which has triggered evacuations and destroyed at least six structures as it burns through timber, brush and grass.
Months of dry weather, a record lack of snow in some areas, hot spells and erratic winds have contributed to blazes in Utah and other parts of the West.
Four firefighters were killed and a fifth was injured after they were overcome by a fast-moving wildfire in Colorado in June.
The firefighters tried to shield themselves by deploying tentlike emergency shelters as flames overran their position.
