Toxicology reports on two Kennewick children showed there were no drugs or alcohol in either their systems when they died.
Benton County Coroner John Hansens released the results of the tests Tuesday, about two months after Kaitlin and Ethan Austin were found shot in their Hansen Park home.
Police are waiting for the results of forensic tests from the state laboratory before discussing the case further.
Kaitlin, 16, was shot several times and her brother Ethan, 12, died of one gunshot wound to his head, authorities said. Police said no one else was involved in the deaths.
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Kaitlin was a junior at Kamiakin High and a pitcher on the state championship softball team. Ethan was a Boy Scout and sixth-grader at Desert Hills Middle School.