Crestline ? Fire officials have finished their investigation into a fatal explosion at a fireworks warehouse but were unable to determine the cause.

Three workers were killed in the Aug. 18 explosion at Fireworks Spectacular’s storage site here. Investigators from the Kansas State Fire Marshal’s Office and the federal Bureau of Alcohol, Tobacco, Firearms and Explosives had been at work since, but the destruction of evidence complicated the inquiry.

“The biggest (obstacle) is just the total devastation of the scene and any evidence that would lead us to the exact event,” said Rose Rozmiarek, chief of investigations for the fire marshal’s office. “We had to rely mostly on witness statements and accounts of what took place.”

Immediately following the event, the investigation focused on a single crate that a worker told authorities had been dropped, leading to the explosion.

Rozmiarek said no evidence backed up that claim.

“All we know is that fireworks were being moved from a storage magazine to a trailer to be transported to a show in St. Louis,” Rozmiarek said.

Faron Trey Robinson, Daniel Lee Groves and Cody Soper were killed in the explosion.