At least 19 fire-fighters have been killed battling a wildfire in Arizona as parts of the western United States continues to bake in scorching temperatures.
The deaths are the greatest loss of life among fire-fighters from a single wildland blaze in the United States in 80 years and are being investigated.
The massive fire about 120km north-west of Phoenix began on Friday (local time) and has spread rapidly amid high heat, low humidity and windy conditions.
The crew were from an elite team tasked with digging a fire line and creating an escape route on Sunday. They were overtaken by swiftly moving flames stoked by near-record high temperatures and high winds. Two others were found alive and flown to a specialist hospital.
Wyatt Devlin, from the Arizona Sheriff's Office, said the crew were on foot when they were caught by the bushfire.
"They were carrying quite a bit of equipment to set up a fire line and that equipment was found at the site. They did have some fire protection blankets which they used. Some were actually found with those blankets over them, but unfortunately it appears the flames and heat were just too much."
About 200 buildings have been destroyed and the towns of Yarnell and Peeples Valley have been evacuated.
Meanwhile, crews are also concerned about more blazes ignited by wayward fireworks launched from backyards to commemorate the Fourth of July holiday on Thursday.
The forecast has offered no relief from soaring temperatures that prompted health warnings and sent scores of people to the hospital with heat-related illness at the weekend, Reuters reports.
Cities in Arizona, California, Nevada, Idaho, Colorado, Utah and Texas recorded temperatures over 100 degrees Fahrenheit (38 degrees Celsius) on Saturday.
Paramedics in Las Vegas, where the temperature hit 115F (46 degrees Celsius), found an elderly man dead in his apartment that did not have air-conditioning.
Many other people were treated for heat-related symptoms, including a man who pulled off a Nevada highway and called 911 to say he felt ill after driving for several hours without air-conditioning. He was hospitalised in a serious condition with heat stroke.
Cities and towns opened air-conditioned "cooling centres" in community centres, homeless shelters and libraries, and warned residents to avoid prolonged exposure to the searing heat.
There are fears that migrants attempting to cross into the US from Mexico would die in the desert. More border agents were added on the American side, a spokesman for the US Border Patrol said.
At least three people who attempted to illegally cross the border into Arizona were found dead this week, and it was likely they had succumbed to the heat, he said.