Racine officials said a fire that killed two girls and injured their two brothers apparently started in a bathroom.
Fire Chief Steven Hansen said investigators are working to determine the cause of the fire.
Firefighters pulled four unconscious children from a first-floor bedroom about 1 a.m. Thursday.
They found an adult male victim in the driveway of the home as they arrived. All were taken to Wheaton All Saints Hospital where the girls, 8-year-old Dalija Scott and 9-year-old Dayja Scott, were pronounced dead.
Two brothers, 5-year-old Luther Patterson and 7-year-old Michael Scott, were transferred to Children's Hospital in Milwaukee. Their conditions were not immediately available.
Hansen said the mother of the children tried rescuing them, but was driven back by smoke and fire and ran to a neighbor for help.