A Feb. 10 explosion at a hyperbaric oxygen chamber at a Florida equine facility that killed one woman and a horse was caused by contact from the horse’s steel shoe with the chamber.

The Marion County Sheriff’s Office concluded in a report that the explosion, at the Kentucky Equine Sports Medicine and Rehabilitation Center (KESMARC) in Ocala, Fla., was an accident. The blast also injured a second woman.

Killed in the explosion was 28-year-old Erica Marshall, who was employed by KESMARC. Sorcha Moneley, 33, of London, England, who was at the facility to look at the oxygen chamber for possible future use in Europe, was injured during the accident.

According to the report, Moneley said the horse in the chamber had steel shoes on his hooves. He began kicking and knocked off a part of the chamber’s protective padding, revealing a metal surface. When the horse kicked again, Moneley said, a spark was created when one of the steel shoes connected with the metal surface