PRESCOTT, Ariz. (AP) - In a heartbreaking sight, a long line of vans from a coroner's office carried the bodies of 19 elite firefighters out of the tiny mountain town of Yarnell on Monday, as the wind-driven wildfire that claimed the men's lives burned out of control.

About 200 more firefighters arrived to the scorching mountains, doubling the number of firefighters battling the blaze, ignited by lightning.

Many of them were wildfire specialists like the 19 fatally trapped Sunday - a group of firefighters known as Hotshots called to face the nation's fiercest wildfires.

With no way out, the Prescott-based crew did what they were trained to do: They unfurled their foil-lined, heat-resistant tarps and rushed to cover themselves. But that last, desperate line of defense couldn't save them.

The deaths of the Granite Mountain Hotshots marked the nation's biggest loss of firefighters in a wildfire in 80 years. Only one member of the 20-person crew survived, and that was because he was moving the unit's truck at the time.

Arizona's governor called it "as dark a day as I can remember" and ordered flags flown at half-staff.

"I know that it is unbearable for many of you, but it also is unbearable for me. I know the pain that everyone is trying to overcome and deal with today," said Gov. Jan Brewer, her voice catching several times as she addressed reporters and residents at Prescott High School in the town of 40,000.

President Barack Obama called Brewer on Monday from Africa and reinforced his commitment to providing necessary federal support to battle the fire that spread to 13 square miles after destroying 50 homes. More than 200 homes were threatened in the town of 700 people.

Obama also offered his administration's help to state officials investigating the tragedy, and predicted it will force government leaders to answer broader questions about how they handle increasingly destructive and deadly wildfires.

Brewer said the blaze "exploded into a firestorm" that overran the crew.

The blaze grew from 200 acres to about 2,000 in a matter of hours.

Southwest incident team leader Clay Templin said the crew and its commanders were following safety protocols, and it appears the fire's erratic nature simply overwhelmed them.

The Hotshot team had spent recent weeks fighting fires in New Mexico and Prescott before being called to Yarnell, entering the smoky wilderness over the weekend with backpacks, chain saws and other heavy gear to remove brush and trees as a heat wave across the Southwest sent temperatures into the triple digits.

Prescott Fire Chief Dan Fraijo said he feared the worst when he received a call Sunday afternoon from someone assigned to the fire.

"All he said was, 'We might have bad news. The entire Hotshot crew deployed their shelters,'" Fraijo said. "When we talk about deploying the shelters, that's an automatic fear, absolutely. That's a last-ditch effort to save yourself when you deploy your shelter."

Arizona Forestry Division spokesman Mike Reichling said all 19 victims had deployed their emergency shelters as they were trained to do.

As a last resort, firefighters are supposed to step into the shelters, lie face down on the ground and pull the fire-resistant fabric completely over themselves. The shelter is designed to reflect heat and trap cool, breathable air inside for a few minutes while a wildfire burns over a person.

But its success depends on firefighters being in a cleared area away from fuels and not in the direct path of a raging inferno of heat and hot gases.

The glue holding the layers of the shelter together begins to come apart around 500 degrees, well above the 300 degrees that would almost immediately kill a person.