Authorities say two brothers are dead after being overcome by fumes in a grain silo on a Central Minnesota farm.

The victims were identified as 47-year-old Curt F. Boesl and 49-year-old Steven T. Boesl.

Authorities say a 12-year-old son of Curt Boesl’s, Alex, also fell ill to the fumes late Saturday morning near Millerville and was taken by air ambulance to a Twin Cities hospital. His condition has not been released.

Authorities say Curt Boesl and his were working in the top of the silo and “were apparently overcome by fumes.”

Another son outside the silo saw what happened and called 911. He also called his uncle, Steven Boesl, who arrived on scene and went to the top of the silo to try and rescue his brother and nephew.

Authorities say Steven Boesl also was “apparently overcome by fumes."

By the time deputies arrived, all three were unconscious. Emergency responders removed them three from the silo.

Ambulance personnel declared Steven Boesl dead at the scene. Curt Boesl died Sunday morning.

Both brothers served as volunteer firefighters in the area, according to KSTP in Minnesota. Curt was the assistant chief and had spent close to 20 years with the department. 

The Millerville Fire Department, where both men worked, was the department that responded to the call. 

"As I drove up my heart just sank," Millerville Fire Chief Rodney Rodgers told KSTP. "It was so sad, and we didn't know what we were coming up on against, and then we found out the gravity of the situation."

GoFundMe page for the family has already raised more than $15,000. 

The Associated Press contributed to this report.