The High Park Fire near Fort Collins is now 10 percent contained. New Mexico's 280,075-acre blaze is now at 51 percent contained.
A Colorado fire has burned an estimated 46,600 acres and continues to grow.
Mandatory evacuations are in place.
The fire has claimed one life: a 62-year old woman found dead in her burned-out cabin.
A crew of 1,000 firefighters are working to control the blaze.
Firefighters have made some progress in containing the biggest wildfire in a decade in Colorado, as federal agencies scramble to help tackle blazes in several western US states.
A crew of 1,000 firefighters were attacking the Colorado fire on Wednesday, while multiple aircraft, including five of the nine heavy air tankers available nationwide, were being used.
"We've got 10 percent containment," Steve Segin, of the Rocky Mountain incident team, said late Tuesday. The fire, the third largest in Colorado's history, has claimed one life.
"This fire still has a lot of potential, but that certainly comes as welcome news," a relieved Larimer County Sheriff Justin Smith told reporters.
Fourteen helicopters, including three Blackhawks from the National Guard, were helping, along with five of the nine Single Engine Air Tankers (SEATs) available in the United States, and five heavy air tankers, it said.
"We have a significant portion of the national fleet here in Colorado," Larimer County Sheriff's Office spokesman Nick Christensen told reporters.
The fire, dubbed the High Park Fire, broke out early Saturday near Fort Collins, about 60 miles (100 kilometers) northwest of Denver.
The fire has burned an estimated 46,600 acres and continues to grow, reported inciweb. It more than doubled to 39,000 acres from Sunday to Monday alone.
The fire has claimed one life, a 62-year-old woman whose remains were found in the ashes of her burned-out cabin. The cause of the fire has been confirmed as lightning.
In Washington, a spokesman said President Barack Obama had called Colorado Governor John Hickenlooper to voice sorrow at "the loss of life as a result of the wildfires and the extensive damage to homes and other structures.
"The president underscored that the administration... stands ready to provide additional resources should they be needed by responders working to protect lives and property," added the White House spokesman.
Hickenlooper meanwhile approved an Executive Order allocating $20 million to containment efforts, saying the fire's "proximity to numerous homes, property, and critical infrastructure poses an imminent danger to life and property."
In neighboring New Mexico, meanwhile, firefighters said better weather conditions on Monday had enabled them to make progress on containing a fire that has ravaged 280,075 acres East of Glenwood.
The New Mexico blaze is now 51 percent contained, as 505 personnel continue to deal with the remaining spot fires, according to an update on the inciweb.org website today.
The Department of Homeland Security meanwhile said it was working closely with emergency services tackling wildfires in a number of other western states, including Arizona, California, Utah and Wyoming.
In all, 19 active large fires were burning in nine states, "including one of the largest wildfires in New Mexico history and one of the largest wildfires in Colorado history," it said.
Some 4,500 extra firefighters have been dispatched by federal agencies, which are also providing emergency funding to help states cope with the costs of tackling the massive blazes.