Local authorities in the US on Thursday were trying to determine the cause of a house explosion that killed three people and injured another in a southern Indiana neighbourhood. <a href="https://www.thenationalnews.com/world/us-news/2022/08/11/indiana-home-blast-kills-three/" target="_blank">The explosion on Wednesday</a> damaged 39 homes in the town of Evansville. Crews on Thursday completed a secondary search of buildings that were left unstable by the explosion and no more victims were found, fire chief Mike Connelly said. “It’s a huge relief, for everybody,” Mr Connelly said. Eleven of the damaged homes were uninhabitable and will have to be demolished, and finding a cause is expected to be a “very tedious process — and lengthy", he said. The names of the dead have not been released and injuries to the fourth victim were not considered life-threatening, Mr Connelly said. Suzanne Dabkowski, a spokeswoman for the Bureau of Alcohol, Tobacco, Firearms and Explosives, said the agency could not give any possible causes of the explosion. Ms Dabkowski said the bureau had explosive specialists and firearms investigators on-site to help with the investigation. The bureau's involvement did not mean there was an intentional or illegal act behind the explosion, she said. “When we come to these types of events we’ve either been asked in by the local fire officials or the state fire marshal for our agents, who have had additional training,” Ms Dabkowski said. “We can be extra hands to help them. Most places aren’t used to seeing a scene of this size.” Evansville is along <a href="https://www.thenationalnews.com/tags/indiana/" target="_blank">Indiana’s</a> border with Kentucky. The blast left debris that included wooden boards, window glass and insulation over a 30-metre radius. CenterPoint Energy, the local gas utility, was last called to the home in January 2018, Mr Connelly said. The utility said it was working with fire officials and other agencies as the investigation continued. It was the second house explosion in the area in about five years. A 2017 explosion killed two people and injured three. Wednesday’s explosion also brought to mind a massive blast in 2012 that destroyed or damaged more than 80 homes in Indianapolis and killed two people. A man was convicted of tampering with a natural gas line at his girlfriend’s home in an attempt to commit insurance fraud.