At approximately 1 pm Pacific Daylight time on Tuesday, April 19th an explosion and fire occurred at a warehouse directly behind Federal Center South near the Duwamish River. Seattle Fire responded to the scene and detected radiation in the immediate vicinity surrounding the warehouse. Upon discovering radiation, Seattle Fire contacted the Washington Department of Health and EPA for assistance. EPA OSC Terada and 4 START contractors arrived on scene at approximately 3 pm to begin evaluating the extent of contamination.