RIVERSIDE, Calif. (KABC) -- A Riverside County Sheriff's Department administration building was evacuated and seven people were decontaminated after a package containing a letter and white powder-like substance was found inside on Monday.The powder was eventually determined to be unbleached cooking flour by a hazmat team, and a criminal investigation is underway.Riverside firefighters responded to the building, located in the 4000 block of Lemon Street, shortly before 9 a.m. for a hazmat involving an unknown substance, according to Bruce Vanderhorst of the City of Riverside Fire Department.Sheriff's officials said a package with a suspicious letter and "white powder" was discovered on the fourth floor administration office.The building was evacuated and seven personnel were decontaminated and transported to a nearby hospital as a precaution, officials said.