“These guys began removing air filters from the intake to the ventilation system of the Physics and Astronomy building at the University of Washington and then measuring the levels of radiation they were emitting. Initially, the filters contained nothing out of the ordinary. Then, sometime between 12pm on 17 March and 2pm on 18 March, the radiation levels began to rise.”
“What they found was small amounts of iodine-131, iodine-132, tellurium-132, iodine-133, cesium-134 and cesium 137.”