The Grant County sheriff's office identified the boy Wednesday as Nathan Sensenig.
Initial reports indicated the boy climbed into the bin on the farm near Lancaster to try to help other family members fix an auger that had become stuck.
But WMTV-TV reports that the sheriff's office says the auger wasn't plugged in. The office says it now appears the boy fell into the bin after climbing a ladder for unknown reasons.
An auger typically is used to move grain from trucks into storage bins.
Lancaster is about 160 miles southwest of Milwaukee.