Rock County authorities are investigating if bone fragments discovered in a fire pit at a Town of Porter home are that of a missing Fitchburg teen. Acting on a tip from the Fitchburg Police Department, sheriff's investigators went to a home at 12016 West Highway 14 Friday afternoon. Over the next day and a half, vidence was collected and the bone fragments tested. They have been determined to be female. The D-N-A is now being tested to see if the remains are 18-year-old Aprina S. Paul. She's been missing since last week Sunday. The sheriff's office says a resident at the home, 29-year-old Nathan C. Middleton has been taken into custody on a probation hold, but not charged with a crime.