IDAHO FALLS, Idaho -

Authorities in eastern Idaho say the object found by two 14-year-old boys in Rigby that exploded and severed one boy's hand was a type of flash-bang grenade not available to civilians and discontinued years ago.

The Jefferson County Sheriff's Office tells the Post Register in a story on Friday that it's trying to determine where the device came from.

Authorities say the boys found the device Wednesday behind a granary on property belonging to the family of one of the boys.

Both boys were taken to Eastern Idaho Regional Medical Center in Idaho Falls.

One was treated and released and the other transferred to Primary Children's Hospital in Salt Lake City, Utah.

Authorities say suspicious objects should be left alone and reported to police.