( CNN ) -- Hundreds of residents ordered out of their homes as a massive wildfire advanced on the suburbs of Fort Collins , Colorado , may be allowed to return Wednesday evening , fire officials said . `` We 're gaining , '' said Bill Hahnenberg , the U.S. Forest Service 's commander for the team battling the High Park wildfire , which has burned 46,600 acres in northern Colorado . The fire , which has claimed at least one life , is estimated to be 10 % contained . About 100 structures are confirmed lost , but hundreds of families are anxiously waiting to hear whether their homes survived . `` This fire 's behavior is starting to diminish , at least in some places , where we can have trained individuals to go in and determine which structures are lost , '' Hahnenberg said during his Wednesday morning media briefing . Hundreds of firefighters have arrived from around the United States to help local departments that have been battling the fire , bringing to 1,000 the number of personnel involved in the fight . The local firefighters , some of whom have lost their own homes , are tired , Hahnenberg said . `` We 're doing our best and have enough resources on board to rotate in and relieve them . '' They 've had `` some success , some failure '' in containing the advance of flames eastward and southward , toward residential areas , he said . Residents should be able to return to two evacuated neighborhoods later Wednesday and perhaps three areas Thursday , said Nick Christensen of the Larimer County Sheriff 's Department . Mark Engle 's family decided not to leave their Colorado home despite the thick smoke billowing through the air outside Tuesday . From a window , he watched deer grazing in his backyard , driven out of the forest by flames that have devoured thousands of acres of land only a few miles away . His children 's backpacks were placed by the door , stuffed with their favorite toys . His family was packed and ready to leave in a hurry , Engle said . But they wanted to stay put , even though authorities have ordered residents in the area to clear out . `` There 's a number of people like myself , ( for whom ) packing up and leaving when you have livestock and animals just is n't as easy as if you have just a house , '' Engle said . First measured at two acres early Saturday , the High Park Fire -- which officials say was caused by lightning -- has grown exponentially in the time since . President Barack Obama telephoned Colorado Gov . John Hickenlooper on Tuesday and said his administration is already making personnel , equipment and federal grants available to the state to help in the effort . The huge plumes of smoke from the High Park fire are visible from miles away , casting a somber shadow even over communities well outside the danger zone . CNN iReporter Dave Thrush , a musician from Denver , posted dramatic pictures of smoke darkening the skies above the Colorado State University campus Sunday . `` The fire is 20 miles from the campus , so no one is in danger there , but the billowing smoke is still very eerie , '' he wrote . Another CNN iReporter , goodline69 , a restaurant server in Lafayette , Colorado , told CNN on Monday : `` It was a beautiful day in Fort Collins with business as usual for many , it seemed , so it was a bit surreal to be watching homes being destroyed from across the reservoir . `` I found myself watching the crowd watch the fire . Heartbreaking . '' Are wildfires near you ? Share your photos and video on CNN iReport , but please stay safe .
NEW : `` We 're gaining , '' CNN incident commander says . NEW : Families may be allowed to return to some neighborhoods Thursday and Wednesday . NEW : The fire has scorched thousands of acres in High Park , Colorado . Thick clouds of smoke are visible from miles around ; Hundreds personnel now involved in fight .