Police say three people were killed and a child is missing after a small boat capsized in the Rhine River between Germany and France.

French and German rescuers are searching for the missing child.

A police official said the boat, which left the German bank of the river Thursday morning carrying four people, sank near the eastern French town of Gerstheim. Two adults and one child were killed, and a child is missing, according to the officer, who was not authorized to be publicly named according to police policy.

It's unclear what caused the sinking. No information was immediately available about the victims' ages or nationalities.

The regional French rescue service for the Bas-Rhin region tweeted that helicopters, divers and police and firefighters are involved in the extensive search.