According to the Fresno Bee, Fresno County health investigators are looking for the food source of an E. coli outbreak that has sickened at least six people who attended private parties in the past two weeks. Five of the six who became ill ate food at the same party on May 19, said Fresno County Health Officer Ed Moreno.  But health workers are talking to people in attendance at two other parties held on the same day to determine if more people have become ill, Moreno said.  A number of food sources are under scrutiny, but the parties were catered by the same company, said Tim Casagrande, the county's director of environmental health.