The explosion happened in a storage room of the Posthotel Morosani shortly after 9 a.m. local time Thursday, regional police spokesman Thomas Hobi told the AP.
He said federal prosecutors are investigating whether the blast has a criminal origin.
The hotel is just over a mile from the main venue of the annual gathering in the Alpine ski resort of Davos. A Forum-related lunch focusing on organized crime, called "Criminals Without Borders" was scheduled at the hotel at noon, with speakers including Colombian President Juan Manuel Santos and Robert Wainwright, the director of Europol, or European Police.
There is tight security at the World Economic Forum as left-wing groups plan to hold a protest this weekend against the annual meeting of political and business leaders and social activists.
Anonymous flyers circulated at a demonstration last week in the northeastern Swiss town of St. Gallen urged activist to "Smash (the) WEF."
The flyer says: "Let us fight together against the unbearable propaganda of capitalism."
In previous years violent activists have stayed away from the chic ski resort and staged violent demonstrations elsewhere in Switzerland instead.