(Sioux Falls, SD) — State officials are releasing more details about the Onida ethanol plant explosion back in July. The incident has now been deemed accidental, according to a report from the South Dakota Department of Public Safety. But investigators say human involvement appears to be a factor. The report also highlighted two separate explosions in different areas of the facility. They were caused when high-proof ethanol vapors escaped a slurry tank and ignited during a restart process from shutting down operations. The ignition source at both locations is still undetermined.