US President Barack Obama urged Americans Saturday to support firefighters battling blazes in the Rocky Mountain state of Colorado that have killed at least two people and left hundreds homeless.

"It's important that we remember what they do each and every single day, and that we continue to provide support to our first responders, our emergency management folks, our firefighters, our military -- everybody who helps secure our liberty and our security each and every day," Obama said in his weekly radio and Internet address.

The comments came after Obama on Friday toured "heartbroken" Colorado neighborhoods torched by rampaging wildfires, viewing charred homes and cars melted by intense heat.

Crews meanwhile were searching for human remains in the ashes of homes destroyed by the Waldo Canyon fire, which spread into the outskirts of the state's second largest city, Colorado Springs, earlier this week.

The inferno destroyed at least 346 houses, forced some 36,000 residents to evacuate, and left at least one person dead, according to officials. It is still threatening some 20,000 homes and 160 commercial buildings.

Obama saw the smoke from nearby fires as he flew into Colorado Springs aboard Air Force One, then inspected some of the devastation and praised the "courage and determination and professionalism" of the firefighters.

In his address, the president said he had seen firefighters working 18 hours a day as they tried to contain the blaze. He also referenced volunteers supplying firefighters with food, water and other resources.

"So, America, I hope you guys remember the folks during these times of need," the president said. "We never know when it might be our community that's threatened, and it's important that we're there for them.

Ahead of his visit, Obama issued a disaster declaration that releases federal emergency funds.

Colorado Springs police chief Peter Carey announced a second death Friday, after a first body was found late Thursday. The remains of both victims were found in the same burned-out house.

"I'm sorry to report the remains of a second human being were discovered," Carey said, his voice breaking. Police spokeswoman Barbara Miller said the pair were believed to be husband and wife.

Officials fear others could have perished in the blaze that started Saturday, and raged out of control on Tuesday and Wednesday whipped up by high winds.

"We've gotten calls from people who say they haven't heard from people," said Miller.

Firefighters made progress in dousing the flames: by late Friday the blaze was 25 percent contained, up from 15 percent earlier in the day, and had burned 17,073 acres (6,830 hectares), up from 16,750 acres Thursday, officials said.

Several other blazes across the mountainous western US state were straining firefighting resources, said fire incident commander Rich Harvey.

The plan is to bring in more heavy equipment where possible "to further enhance our ability to put muscle down on the ground in front of this fire and keep it in its containment lines," Harvey said.

Some 33 crews were fighting the blazes with 76 engines and 11 bulldozers. Three helicopters had dropped 384,205 gallons of water.

Officials in Colorado Springs met privately on Thursday night with distressed evacuees -- many of whom fled with no time to collect their belongings.

"You never think it's going to happen to you," Rebekah Largent told reporters after leaving the meeting.

Her husband Byron said residents looked at lists of homes street-by-street.

"If your address wasn't there, that meant it (the house) was intact. And so you just look at the paper and you see destroyed, destroyed, destroyed, and you see one damaged and then destroyed, destroyed, destroyed," he said.

Bus tours of the ravaged areas are being organized for residents on Sunday, to allow them to see their homes.

"One of the things very important to them is that they get back to see their property," although residents won't be able to get out and look closely because the area remains dangerous, said Colorado Springs mayoral aide Steve Cox.

The Waldo Canyon blaze forced the evacuation of the nearby US Air Force Academy, where cadets joined fire crews in protecting their barracks and other buildings as the fire swallowed 10 acres of the academy's land.

Summer wildfires are common in the mountains of arid Colorado but rarely burst into residential areas, as the Waldo Canyon Fire did earlier this week. It is not yet known what sparked the blaze.

Record high temperatures, extremely low humidity and wind gusts of up to 60 miles (100 kilometers) an hour have fueled fires across the American West, where an unusually mild and dry winter left widespread tinder-like conditions.