A toddler was pronounced dead at the hospital Monday morning after she was found unresponsive in the river 400 yards away from the cabin in Big Thompson Canyon where her family had last seen her.

David Moore, a spokesperson for the Larimer County Sheriff’s Office, says first responders received a 911 call from the 23-month-old’s mother at 9:23 a.m.

Moore says the mother told investigators she was asleep inside the cabin off US 34 near Drake when she says she woke up and the door was ajar. The young child was gone.

Thirty minutes later, Moore says one of the first responders called to the scene pulled the child from the water downriver.

Investigators are working to determine what led up to the child’s disappearance and if any foul play was involved, Moore said.

The coroner’s office has not yet identified the toddler by name or said how she died.