An investigator from the state Fire Marshal’s Office is in northern Iowa this morning, trying to determine the cause of a fire that killed three children and their grandfather. The four died in a weekend housefire in the Winnebago County town of Scarville. 52-year-old Michael Awe & three of his grandchildren, ages 4, 6 and 7 all died in the Saturday fire, the cause of which is still unknown. Winnebago County Sheriff Tom Lilliquist says the mother of the children, Michelle Janka, returned home to find the house full of smoke early Saturday morning.Sheriff Lilliquist says fire crews from the surrounding area & Minnesota were called to fight the blaze.Lilliquist says he’s especially disturbed by the number of people who are dying in fires.It’s the third fire that killed at least four Iowans in recent months — three children and three firemen were killed in a December blaze in Keokuk, and last month, a Mount Ayr man & three of his children died in another pre-dawn house fire.