Davos, Jan 27 (Agencies): Swiss police on Thursday said a small blast shattered two windows but caused no injuries at the Posthotel Morosani where the World Economic Forum is being held.

The explosion happened in a storage room of the hotel near where top business and political leaders were attending the forum, shortly after 9 am local time (0800 GMT) on Thursday, regional police spokesman Thomas Hobi said.

He said federal prosecutors are investigating whether the blast has a criminal origin.

The hotel is just over a mile (around 2 kilometers) 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.

Swiss media say an anti-WEF group threatened in an e-mail to attack the hotel with fireworks.

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.

In previous years violent activists have stayed away from the chic ski resort and staged violent demonstrations elsewhere in Switzerland instead.