State investigators have announced the cause of an explosion that killed three employees of Jimbos Auto Repair in Hillsboro.On November 28, 2023, at 5:02 p.m., surveillance video shows a fiery blast leveling much of the auto sho p to the ground in a plum of black smoke.The cause of the explosion is the 100-pound propane gas cylinder was overfilled with propane at Dance's Steel and Farm Supply on November 28, 2023, (the same day as the deadly explosion) by Dance's Steel and Farm Supply employee around 1 - 1:30 p.m., the incident report concludes on page 126.While the employee is named in the report repeatedly, WCPO is not naming him because he has not been charged with a crime.Listen to parts of the employee's interview with investigators: Investigators share cause of deadly Hillsboro auto shop explosionInvestigators concluded the ruptured propane tank should have never been filled. The report states the tank was manufactured in 1950, re-certified in 1978, and had a malfunctioning safety valve. It was overfilled outside on a cold day (the weather at the time of the explosion was 27) and then brought inside the auto repair shop. Because the temperature was warmer inside, the gas expanded due to an increase in the ambient temperature, the report summarizes from a Fire and Materials Research Laboratory that inspected the tank.The initial rupture released a dense cloud of propane vapor into the auto shop, which ignited when it came into contact with the open flame of a ceiling-mounted furnace, leading to the deadly fireball.In a possible charging affidavit, the state fire marshal writes the tank still had the transportation cap attached (from just being filled) and was not hooked up or in use. In their report, state fire officials wrote that an employee at Dances Steel and Farm Supply, about three miles from the repair shop, filled four, 100-pound propane tanks for the owner of Jimbos, James Chambers.Beyond the one that was placed in the auto repair shop, the other three were taken back to Chambers' personal property, the report states.The following day, Chambers recorded a video of the tanks off-gassing, which continued for over two weeks. Who filled the tanks?Dances employees reported that the security cameras at the business "stopped working" on the day of the explosion.Based on testimony from Chambers and another witness, investigators identified the employee who filled the tank that exploded at the auto repair shop.Evidence discovered during the investigation was that [employee], nor Dances Steel and Farm Supply were tracking or measuring how much propane was being dispensed into each tank as a standard business practice, and in particular, the grey, 100-pound, ruptured propane cylinder in question.The investigators said the employee remembers everything about the day of the propane filling, November 28, 2023, referring to the specific details of Chambers, his passenger, the way the four (4) 100-pound propane tanks/cylinders were stacked in the bed of Chambers pickup truck, and the debris in the bed of the truck, except the filling the tanks.You didn't fill them. Or you don't remember filling them? the investigator asked the employee on April 22, 2024 in a recorded interview.I didn't fill em, because [sic] Id remember, the employee responded.I think you would, the investigator said.Investigators also noted that two days after the fire, they had to stop the same employee from filling propane tanks that were either expired or defective. Case closedInvestigator J. Cunningham writes that on February 28, 2025, Hillsboro City Prosecutor Randalyn Worley and special counsel David Kelly told investigators that no criminal charges would be filed against the employee.Hillsboro City Law Director, Randalyn Worley, said in a statement to WCPO: My office has thoroughly reviewed the investigation and has determined that the elements of negligent homicide cannot be met through the evidence presented by the State Fire Marshal."I want to extend my deepest condolences to the families and individuals affected by the tragic explosion, Worley added.Based on no action by the Hillsboro City Law Director, the State Fire Marshals Office officially closed the case.Watch our original reporting on the blast: 3 dead, 1 hospitalized after explosion in Ohio cityThis story was initially reported by a journalist and has been, in part, converted to this platform with the assistance of AI. Our editorial team verifies all reporting on all platforms for fairness and accuracy. ...read more read less