The activity, popular among young people, involves using different methods to cut off the oxygen supply in order to replicate the experience of losing consciousness.
Police initially believed that the boy had taken his own life but have reassessed this theory having heard the father’s version of events.
“The only version we have is the dad’s,” police spokesman Jan-Inge Bexell told Sundsvalls Tidning.
Bexell added that the police did not suspect foul play.
The choking game phenomenon has remained popular among children worldwide despite repeated warnings. A number of deaths have been reported in the United States, while in Sweden children have been found unconscious after indulging in the activity.