Investigators continue looking through a burned out Keokuk apartment building, trying to determine what caused the Wednesday morning fire that killed three firefighters and three children. Keokuk Fire Chief Mark Wessel identified the fallen firefighters in a news conference with reporters.They are assistant chief, Dave McNally, a 25-year veteran of the department with a wife and three children, firefighter Jason Biting, a six-year veteran with a wife and three children and firefighter Nate Tuck a four-year veteran of the department with a wife and two children. Wessel wouldn’t say what may have caused the fire.The State Fire Marshal is leading the investigation.The mother of the three dead children and one other child are hospitalized at University Hospitals in Iowa City. Officials say they’re in fair condition.