Frankfurt police say they have found evidence that an American student who disappeared in November most likely fell into the city's Main River.

Police said in a statement Friday that dogs traced the trail of 22-year-old Devon Hollahan of Scottsdale, Arizona to the banks of the river, and that authorities found a shoe believed to be his in the waters.

Police say: "with these clues, at the moment it seems likely that Devon Hollahan fell into the Main."

Hollahan, who had been teaching English in Prague since July, was traveling back to a hostel with a friend, who stopped to ask for directions. When the friend turned back around, Hollahan was gone.

The U.S. consulate in Frankfurt and local police are both involved in the search for Hollahan, who was last seen Nov. 21.