Griswold, IA – Authorities have determined a propane explosion in Griswold was caused by a leak in a ruptured rubber hose.

The June 3 explosion at the Pelgrow company injured four people who worked at the business. All were near a gas grill when the explosion occurred.

Officials from the Cass County sheriff’s office and State Fire Marshal’s Office on Monday blamed the explosion on a hose leading from steel piping to a pump. Investigators cited three possible ignition sources: a gas-fired water heater, the motor of the propane pump or static electricity.