Police said a "small explosion" went off on Thursday in a hotel at the Swiss alpine resort of Davos, where global political and business leaders have gathered for the World Economic Forum.
"A small explosion of unknown origin," occurred in the basement of the Morosani Posthotel in Davos, said a cantonal police spokesman.
"No one was injured and material damages were minimal," he added.
Federal prosecutors will examine the cause of the explosion, he said.
Some 2,500 political and industry leaders are gathered in the small alpine village for the forum which ends on Sunday.