Correction: A previously version of this story incorrectly listed the company the two victims worked for.

Two workers who became trapped inside an 80-foot farm silo that they were repairing in eastern South Dakota have Johnathan Walkerdied, presumably killed by toxic gas.

The accident occurred shortly before noon on Saturday at a rural farm in the small town of Volga, the Brookings County Sheriff’s Office said in a Facebook post on Monday. The victims were working on a damaged roof above a nearly full 80-foot-tall silo.

Larry Dalzell, a 51-year-old from central Tennessee, and Randi Vandekieft, a 41-year-old from central Georgia, were both recovered from the silo and later pronounced dead. The sheriff's office said the two were "believed to have been overtaken by toxic gas."

It's unclear how the two became trapped in the silo. The Brookings County Sheriff’s Office is investigating the deaths.

USA TODAY is working to identify the company the men worked for.