Swiss police said Monday they had broken off the search for a 12-year-old American boy who disappeared last week near Switzerland's popular resort of Interlaken.

A shoe found at the exit of the gorge where the Greenwood, Indiana, boy was hiking Friday with his family could belong to him, a spokeswoman for the Bernese cantonal (state) police said. Rescuers had been searching for Noah Kriese near the Truemmelbach waterfalls, where visitors can walk through a mountain to see cascades crashing from inside.

"We searched until last light Sunday, and this morning we did a final search at 6 a.m.," Ursula Stauffer told The Associated Press. "We didn't find him."

She said police had ended their search. "Instead, we will be doing spot checks at key points in the gorge," Stauffer said.

Police have declined to identify the boy by name because of Swiss privacy rules.

Jennifer Duffy, who described herself as a friend of the Kriese family, said Noah's parents were still holding out hope of finding their son alive.

"While we have no confirmation of Noah's whereabouts, we are hoping for the best," Duffy said in a statement she read out to the AP in Indianapolis. "We ask that people continue to keep Noah and his family in their thoughts and prayers as we, his family, certainly are."

Kriese was visiting the Truemmelbach falls, about 30 miles southeast of the Swiss capital, Bern, with his mother and her family, Duffy said.

Kriese's father has traveled to Switzerland to assist the search efforts, she added.

Duffy, of Greenwood, about 10 miles south of Indianapolis, declined to elaborate beyond the statement.

The Truemmelbach falls, which drain glacial waters from the country's famous Eiger, Moench and Jungfrau mountains, are part of the UNESCO world heritage site for Switzerland's Jungfrau-Aletsch-Bietschhorn glaciers. Thousands of tourists visit year to see 5,000 gallons of water rage through the rock each second.

The falls are extremely narrow and dark, and can be reached by an elevator inside the mountain. But walking paths are guarded by rails and keep visitors protected from any direct contact with the falling water.

Rescuers have been unable to enter the water itself because of strong currents. Police said other hikers claimed to have seen a person in the rapids around the time of the boy's disappearance, and officials are still appealing for witnesses who might have information about his whereabouts.