Police posted photos of the boy on a missing persons Web site but declined to identify him by name because of Swiss privacy rules.
Stauffer told The Associated Press the boy and his family were from Indiana but did not elaborate.
She said police and rescuers were searching the gorge, which has a number of waterfalls, but had not been able to enter the water because of strong currents caused by glacial meltwater. Police said other hikers claimed to have seen a person in the rapids around the time of the boy's disappearance.
The Truemmelbach Falls are part of the UNESCO world heritage site for the massive Jungfrau-Aletsch-Bietschhorn glaciers. The falls are extremely narrow and dark, flowing inside the rock, and are reached by an elevator inside the mountain.
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