Search and recovery operations are continuing at the Lake Springfield dam after four people were swept over the structure on Sunday.
The Springfield Fire Department says one juvenile was rescued, while two teenagers have been found dead and one adult remains missing.
The Boone County Fire Protection District has deployed specialized K-9 search teams and personnel to assist local agencies.
Officials say the teams were requested directly by Springfield fire crews and began operations Wednesday morning.
Crews, working alongside multiple regional agencies, continue searching the river area for the remaining missing person.
Investigators say the group was on a kayak and inflatable tubes connected together when they went over the dam.
The incident remains under investigation.