Police in the canton of Aargau issued a call for help at the weekend after a two-year-old boy vanished while on an outing with his father along the Reuss River in Windisch, near Baden.
The toddler disappeared around 8.30pm on Saturday near the confluence of the Reuss and Aare rivers, police said in a statement.
The weather was deteriorating at the time, police said.
A Rega emergency rescue helicopter scoured the area, along with a search dog but were unable to find the child.
The blonde-haired tot was wearing a yellow, blue and white striped sweater, blue jeans and sneakers, police said.
Anyone with information about his whereabouts was asked to contact Aargau police on 062 835 81 81.
The incident occurred a week after another two-year-old boy disappeared while with his parents at a baptism ceremony at a Catholic church in Wattwil in the canton of Saint Gallen on April 18th.
Police launched an intensive search operation in the village and along the nearby Chur River without success, although one of the boy’s shoes was found.