By Tim Gaynor
PRESCOTT, Ariz., July 2 (Reuters) - Weary crews on Tuesday looked for a break in the weather to gain ground against a fierce Arizona wildfire that has already killed 19 of their fellow firefighters in the worst wildland fire tragedy in 80 years.
Fire managers say the so-called Yarnell Hills fire, which has already charred nearly 8,400 acres (3,400 hectares) of tinder-dry chaparral and grasslands northwest of Phoenix, was zero percent contained as darkness fell on Monday evening.
The lightning-sparked blaze, which broke out on Friday afternoon near the community of Yarnell, has torched some 200 structures, most of them homes.
On Sunday, an elite squad of 19 firefighters died in the fire after they were outflanked and engulfed by wind-whipped flames in seconds, before some could scramble into cocoon-like personal shelters.
Details of Sunday's deaths of all but one member of the specially trained, 20-man Granite Mountain Hotshots were still sketchy as an investigation was launched into how the disaster unfolded.
Fire officials said the fallen men, most in their 20s, were victims of a highly volatile mix of erratic, gale-force winds, low humidity, a sweltering heat wave and thick, drought-parched brush that had not burned in some 40 years.
They were trapped as a wind storm kicked up and the fire suddenly exploded on Sunday, said Peter Andersen, a former Yarnell fire chief who was helping the firefighting effort.
"The smoke had turned and was blowing back on us," Andersen said. "It looked almost like a smoke tornado, and the winds were going every which way."
'NOTHING THEY COULD DO'
The powerful gusts abruptly split the fire, driving it in two directions, then pushing flames back in on the hotshot crew, who were working on one flank of the fire front, he said.
Sunday's disaster in Arizona marks the highest death toll among firefighters from a U.S. wildland blaze since 29 men died battling the Griffith Park fire of 1933 in Los Angeles, according to the National Fire Protection Association.
The firefighters deployed their personal shelters, capsule-like devices designed to deflect heat and trap breathable air, in a last-ditch effort to survive, officials said.
Andersen said some of the men on the ground made it into their shelters, according to an account relayed by a ranger helicopter crew flying over the area.
"There was nothing they (helicopter crew) could do to get to them," he said.
The deaths brought an outpouring of tributes from political leaders, including U.S. President Barack Obama, who is on an official trip to Africa. Arizona Governor Jan Brewer called the deaths "one of our state's darkest, most devastating days" and ordered state flags flown at half staff through Wednesday.
Authorities who ordered the evacuation of Yarnell and the adjoining town of Peeples Valley say that they were proceeding cautiously following Sunday's tragic events and hoped that strong winds that have driven the blaze would diminish on Tuesday.
"We need the winds to not pick up enough so we can safely move crews around," fire spokeswoman Carrie Templin said.
The Yarnell Hills blaze was one of dozens of wildfires in several western U.S. states in recent weeks in what experts say could be one of the worst fire seasons on record. (Additional reporting by David Schwartz and Dan Whitcomb; Writing by Dan Whitcomb and Steve Gorman; Editing by Lisa Shumaker)