Department of Homeland Security Secretary Janet Napolitano urged residents in the area to heed local authorities' instructions, while lamenting the loss of so many firefighters.
"Today, our thoughts and prayers go out to the families and loved ones of the 19 firefighters who lost their lives in the line of duty," she said in a written statement. "As thousands of their colleagues continue to fight wildfires across Arizona and the West, the Department of Homeland Security and FEMA are working closely with our federal partners including the Forest Service and the Department of Interior, to support state and local efforts."
President Barack Obama also lauded the efforts of the fallen firefighters, saying their deaths are heartbreaking and "our thoughts and prayers go out" to their families. His administration stands ready to help in any way necessary, he said.
"They were heroes -- highly skilled professionals who, like so many across our country do every day, selflessly put themselves in harm's way to protect the lives and property of fellow citizens they would never meet," he said in an earlier statement.
Brewer, who was to visit Prescott on Monday, said the loss marked "as dark a day as I can remember." She has ordered state flags be flown at half-staff from sunrise Monday to sunset Wednesday, and issued an emergency declaration that will make $200,000 available for response and recovery, while authorizing mobilization of the National Guard, if necessary.
"It may be days or longer before an investigation reveals how this tragedy occurred, but the essence we already know in our hearts: fighting fires is dangerous work," she said.
"When a tragedy like this strikes, all we can do is offer our eternal gratitude to the fallen, and prayers for the families and friends left behind."
Fraijo said the firefighters who died were exceptionally dedicated to their jobs.
"These are the guys that will go out there with 40, 50 pounds of equipment and walk five miles. They'll sleep out there as they try to develop fire lines" to protect homes, Fraijo said.
Before the 19 deaths in Arizona, 43 firefighters had been killed so far in 2013, according to the U.S. Fire Administration. A total of 83 firefighters died last year while on duty.
A Facebook page in memory of the Arizona firefighters garnered more than 120,000 "likes" in less than 10 hours.
"Such a tragic loss," one person wrote. "My heart aches for these brave souls, and for their families and friends."