HOWARD, Wis. (WBAY) - The Brown County Sheriff’s Office is closing its investigation into a fire that killed twin sisters in Howard last November. Authorities determined the fatal fire was caused by gasoline containers in the home on Rockwell Rd. The sheriff’s office says three damaged containers were stored in an unsafe manner, introducing “ignitable vapors” into the home. The vapors ignited in a small explosion that set off the fire. Haley Ann Fritsch and Kayla Lynn Fritsch, 26, died in the house.