Investigators believe holes in the top of a muffler ignited the floorboard and interior of a vehicle Tuesday on Interstate 86 in the town of Erwin, Steuben County, killing a 4-week-old infant and her 18-month-old sister, the Rochester Democrat & Chronicle reports.
          The infant, Sinaya Beam, and her sister, Izzybella, both died in a fire that broke out in the back seat of the 1999 Kia Sportage driven by their mother, Melissa Johns, 25, of Savona, the newspaper said. Johns was driving home from Guthrie Clinic, in Sayre, where the infant had her first checkup Tuesday, family members told the newspaper.
          State Police Investigator Chris Wilkinson said troopers suspect the fire started when welded spots on the top of the muffler eroded, allowing hot exhaust gases to escape, burn through the floorboard and ignite the interior of the car.