( CNN ) -- Firefighters made inroads into the massive wildfire in eastern Arizona Sunday , as authorities said the threat of spreading flames had decreased enough to allow thousands of residents in some of the hardest-hit areas to return home . `` After consulting with fire officials , it has been determined that the fire risk has diminished enough that it will no longer be a threat to the citizens of the towns , '' said Cmdr . Webb Hogle of the Apache County Sheriff 's Office . But he said smoke from the wildfire `` still poses serious health hazards '' in Springerville , Eagar and South Fork , where authorities expect thousands to return home after evacuating . `` If they return , they do so at their own risk , '' he added . The 15-day-old blaze in eastern Arizona was 10 % contained , fire officials said Sunday evening , up from 6 % late Saturday . Still , the wildfire inched closer to becoming the worst fire in the state 's history . The second-largest blaze had scorched 443,989 acres , firefighters said Sunday , an area bigger than most of the largest cities in the United States . The so-called Wallow fire is 24,649 acres shy of matching the Rodeo/Chediski wildfire of 2002 , Arizona 's biggest . Firefighters said they are making progress as they dig trenches , set their own fires to take away natural fuels from the advancing blaze and dump retardants from the air on the flames . It `` has been chasing us around , but after today we 're feeling very optimistic , '' Jerome MacDonald , operations chief for the Southwest Interagency Incident Management team fighting the fire , told reporters late Saturday . The fire broke out May 29 in the Apache National Forest . Air quality for much of New Mexico and eastern Arizona was expected to worsen because of wildfires , the New Mexico health and environment officials said . Heavy smoke could affect those in sensitive groups , including children , pregnant woman , asthma sufferers and people with lung and heart diseases , the New Mexico Environment Department said . The National Weather Service said smoke plumes from Arizona wildfires will continue moving toward Santa Fe and Albuquerque , New Mexico . Heavy smoke has permeated communities around the Arizona blaze . `` We have not seen the sun clearly for several days , '' said Rita Baysinger , a spokeswoman for the Southwest Interagency Incident Management team . MacDonald said changing winds are likely to start clearing out the smoke . `` All the smoke from the fire has basically been funneling through Eagar in the valley and it settles there in the morning , '' MacDonald said . `` I do n't expect the same kind of smoky conditions over the next couple of days . '' At least 9,114 people were evacuated from Springerville , Eagar , Nutrioso , Alpine , Greer and surrounding areas . The wildfire has consumed 29 homes , 22 of them in the evacuated city of Greer . CNN 's Phil Gast and journalist Craig Johnson contributed to this report .
NEW : The Wallow fire has scorched 443,989 acres in eastern Arizona . NEW : Officials say the blaze is 10 % contained . A commander says residents in Springerville and Eagar can return home `` at their own risk '' Arizona 's worst wildfire burned 468,638 acres in 2002 .