UPDATE: They have been found and are safe.
The Tennessee Bureau of Investigation has issued an Amber Alert.
"We need your help to find 5-year-old Koraleigh Simon and 6-year-old Kayson Jones, who are missing from Erwin," TBI officials said. "Both children were last seen earlier today and may be with Jason Simon, their non-custodial father. He is wanted by the Erwin Police Department on kidnapping charges. At this time, we do not have a vehicle description to pass along. If you have information regarding the whereabouts of Koraleigh, Kayson, or Jason Simon, please call 1-800-TBI-FIND. We will update this post with any new details as we can."