A man died after breathing toxic fumes Saturday in central Minnesota while trying to save his brother and nephew, who had fallen unconscious inside of a silo, according to the Douglas County Sheriff's Office.

Sheriff Troy Wolbersen said in a news release that the man died at the scene. His name has not been released.

The man's brother was taken by helicopter to a hospital to St. Cloud and his nephew was flown to Children's Hospital in Minneapolis; their conditions weren't immediately known on Saturday evening.

Wolbersen wrote that the father and son were working "in the top of the silo" near Millerville when they were overcome by fumes. The town of about 100 residents is 150 miles northwest of Minneapolis, between Fergus Falls and Alexandria. Another son noticed that the two were down and called 911; he also called his uncle, who lived nearby and who, on arriving, climbed into the silo to try "to extricate the father and son," according to the release.

"The uncle arrived on scene and entered the top of the silo to extricate the father and son," the release read. "The uncle was then apparently overcome by fumes."

By the time deputies arrived, all three victims were unconscious.

Officials said an autopsy will be performed by the Midwest Medical Examiner's Office.

According to data analyzed by Purdue University, 15 farmworkers died in grain bin accidents last year, with most silo deaths involving people who asphyxiate or are crushed by falling grain. But another danger is so-called silo fumes, which are formed during fermentation of silage stored in a grain bin that can produce such gases as nitrogen dioxide.