The two men killed in an industrial accident at MagnaGro International on April 1 died of asphyxiation, official reports show.

According to their autopsy reports, Brandon Price and Roy Hillebert were overcome by fumes while cleaning a storage tank containing cane molasses. The Douglas County and Shawnee County coroner’s offices performed the autopsies.

According to both reports, Price, 25, climbed down into the tank, then began to have trouble breathing. Andy Cooper, a nearby co-worker, heard Price fall and went into the tank to retrieve him. When he realized the air was impossible to breathe, Cooper climbed out of the tank and said he was going to get a fan.

Roy Hillebert, 51, then climbed into the tank to rescue Price, but was also overcome by the fumes and fell in.

When Cooper returned he noticed the two men lying at the bottom. Using a saw, he cut a hole in the side of the tank and went in to retrieve both men, but the fumes caused him to collapse shortly after he entered. Lawrence-Douglas County Fire Medical crews arrived shortly after and pulled all three men out of the tank. Price was pronounced dead at the scene and Hillebert died at Lawrence Memorial Hospital.

A toxicology report found traces of methamphetamines in Hillebert’s system, but the drug did not cause his asphyxiation and would have only played a minor role in the speed of his collapse. Hillebert also had a heart condition.