Sioux City Police are investigating an assault that sent one person to the hospital with injuries early Friday morning.
Police say an unconscious male victim was found lying on the ground at 522 4th Street in the downtown area just before 1am.
The victim had suffered what was described as a serious head injury.
Police say a suspect left the area on foot and could not be located by responding officers.
The male victim was transported to Mercy Medical Center.
His identity is not being released at this time and the suspect is unknown.
The incident remains under investigation.