BROTHERTOWN, Wis. (AP) – Authorities say carbon monoxide poisoning caused the death of a Chilton woman in an ice shanty on Lake Winnebago.  An autopsy on 30-year-old Sara Meyer was performed Monday. Meyer was declared dead at the shanty Saturday. A 37-year-old man who was found unresponsive in the shelter was taken to St. Elizabeth Hospital in Appleton. His name and condition have not been released.  The Calumet County sheriff’s office says the investigation is continuing, but foul play is not suspected.  Authorities are urging anglers to use caution when heating their fishing shanties, and to make sure their heating equipment is in good working order and vented properly.