(Tracy, MN) -- A mother and her three daughters were injured after their home in Tracy exploded Saturday morning. Neighbors heard the explosion and witnesses saw the mother and her two-year-old daughter running from the house, while another daughter, seven-years-old, ran out a separate door. A neighbor was able to rescue a two-month-old who was in her crib inside the house. All four victims were taken to a nearby hospital, then airlifted to Regions Hospital to be treated for burns. The mother remains in critical condition. The cause of the explosion is under investigation.