US President Barack Obama has said that the deaths of 19 firefighters who died battling an Arizona wildfire are a heartbreaking reminder that emergency personnel put their lives on the line every day while rushing towards danger.
Obama, who spoke from Africa on Monday, added that America's thoughts and prayers go out to their families.
"We are heartbroken about what happened," he said.
The firefighters, members of an elite crew fighting a forest fire northwest of Phoenix, were overtaken on Sunday by a fast-moving blazed fuelled by hot winds. Some 200 homes were also destroyed.
The Granite Mountain Hotshots from the the Prescott Fire Department were killed after the wildfire trapped them near Yarnell, about 80 miles northwest of Phoenix.
Meanwhile, people in the town of Prescott have held a memorial service as officials expressed concern that the fires are still raging.
"It had to be a perfect storm in order for this to happen," Prescott Fire Department spokesman Wade Ward told local media on Monday. "Their situational awareness and their training was at such a high level that it's unimaginable that this has even happened."
The blaze was raging unchecked on Monday after burning about 8,400 acres of tinder-dry chaparral and grasslands. It was sparked by lightning on Friday, Arizona state fire officials said.
Ward said the men had put up fire shelters, a tent-like safety device designed to deflect heat and trap breathable air, in a last-ditch effort to survive.
|The Granite Mountain Hotshots [AP]
Prescott Fire Chief Dan Fraijo said late on Sunday one member of the 20-man crew had been in a separate location and survived. There was no immediate information on his condition.
The Yarnell Hills fire marks the greatest loss of life among firefighters from a US wildland blaze since 29 men died battling the Griffith Park fire of 1933 in Los Angeles, according to the National Fire Protection Association.
The Hotshots were highly trained firefighters with rigorous fitness standards. They were required to take an 80-hour critical training course and refresher yearly, according to the group's website.
"Our common bond is our love of hard work and arduous adventure," the website says.
The Yarnell Hill fire has been stoked by strong, dry winds and a heat wave that has baked the western United States in more than 40C temperatures.