Authorities say a natural gas explosion causing fires that destroyed three houses and a barn in southern Ohio apparently was ignited when a pipeline failed.
Investigators said Thursday that they believe a spark from debris, static electricity or nearby power transformers likely ignited the gas. But they can't determine the exact source.
Investigators found no evidence of criminal intent in Wednesday's explosion near Glouster. It was felt as far as 12 miles away.
They say the buildings were destroyed by fires from radiant heat and not by the explosion. Two people were treated for minor injuries.
The state fire marshal's and Morgan County sheriff's offices have turned their investigations over to the U.S. Department of Transportation. The Ohio Environmental Protection Agency will monitor for any potential effect on the environment.