Authorities remain stumped as to what killed Ellen Chung, her husband Jonathan Gerrish, their 1-year-old daughter, and their dog during a hike in Mariposa County, California—but they’re slowly ruling out potential causes of death. After weeks of toxicology tests, some of which are still pending, the Mariposa County Sheriff’s Office announced that the family did not die by “gun or other types of weapons, lightning strike, carbon monoxide, carbon dioxide, cyanide exposure, illegal drugs or alcohol, or suicide.” However, toxic algae and heat—it was between 107 and 109 degrees that day—are two possibilities authorities have not yet ruled out. “As we navigate through this investigation with the family, we will later share our findings with the public,” said Sheriff Jeremy Briese.