A bucket of possibly — but not very — radioactive kitty litter was the culprit in a hazardous material response Tuesday night outside a Capitol Hill apartment building. Seattle Fire responded to the report of a suspicious bucket marked as containing hazardous material outside the E Harrison building around 6:15 PM. According to SFD, responding crew members were “investigating an unknown substance located in a small container/bucket.” It took about 30 minutes but SFD was able to conduct tests and observations to determine the contents of the bucket were unlikely to be harmful. “HAZMAT crews determined the substance to be cat litter from a pet receiving radiation treatment,” SFD reported from the scene.