Australia wildfires slowly being controlled 호주 산불 이 서서히 통제 되 어 지 고 있 다 . KINGLAKE , Australia ( CNN ) -- The wildfires that have roared through southeast Australia for nearly a week were slowly coming under control Friday , as investigators continued the search for who may have set some of the deadly blazes . A dirt track runs through the burnt out forest in the Kinglake region of Victoria state . 2 of 2 more photos » The Country Fire Authority said the number of fires burning had dropped to 21 from about 35 on Thursday . While " the threat will remain for weeks to come , " a spokesman said no towns were under threat Friday morning and that good weather had allowed firefighters to build containment lines around the fires . Meanwhile , more than 150 detectives were working on an arson investigation , authorities said . Two men who were arrested for " suspicious behavior " on Thursday were released without charges . " We are satisfied with their explanation and don ' t expect to talk to them again , " Victoria state police inspector Peter Sheppard said . Firefighters have battled blazes since Saturday -- including several new fires that broke out Tuesday night , which officials said almost certainly were the result of arson . See map of fire - hit areas » Don ' t MissSurvivors frustrated as fires smolderBlog : ' Rural Australians are a tough bunch ' BackStory : Face - to - face with wildfiresiReport . com : Send your photos , videos and storiesThe official death toll from the fires has remained at 181 for the past two days . But government officials say that number could reach as high as 300 based on the number of people missing and number of homes destroyed . iReport . com : Raging fire approaches homeSheppard said the tally is not being updated as frequently because it ' s become harder to verify fatalities from the fires -- which have destroyed more than 1 , 800 homes and displaced about 7 , 000 people . " Initially it was a fairly straitforward process -- bodies were in cars , on sides of roads , " he said . " Now , the search is through buildings . Many have collapsed . " Watch profiles of lucky animals that survived the fires » He said that in the town of Marysville , which was hard - hit by the wildfires , bodies are believed to be in a hotel but firefighters cannot get access to it . iReport . com : Wildfires tear through Victoria state » On Thursday , Prime Minister Kevin Rudd announced to parliament that the government will hold a memorial service and national day of mourning for victims of the fires . He said the government is working with the nation ' s Council of Churches to determine the day .