DAVOS, Switzerland — A small blast shattered two windows but caused no injuries at a hotel used by top business and political leaders attending the World Economic Forum, Swiss police said Thursday.
The incident occurred on the day French President Nicolas Sarkozy, British Deputy Prime Minister Nick Clegg and former U.S. President Bill Clinton were due to take the stage at the annual gathering in the Swiss Alpine town of Davos.
Forum organizers said in a statement that the explosion was caused by a firework.
An anonymous posting on the website indymedia.ch claimed responsibility for the attack on the Posthotel Morosani, saying it was directed at Swiss government officials and senior executives of Swiss bank UBS staying at the hotel. Its authenticity couldn't immediately be confirmed.
The Swiss federal prosecutors office said in a statement that it is investigating the incident but provided no further information "for tactical reasons."
The explosion happened in a hotel storage room shortly after 9 a.m. local time (0800 GMT) Thursday, regional police spokesman Thomas Hobi told the AP. The hotel did not comment.
The anonymous claim of responsibility said "two pyrotechnical devices and sugar" were used to cause the blast.
The hotel is just over a mile (around 2 kilometers) from the main venue of the annual gathering in the Alpine ski resort.
There was little disruption to the hotel and its activities beyond an increased security presence at the hotel's entrance. Guests, journalists and others were filing through a security scanner that was installed before Thursday's incident.
A Forum-related lunch focusing on organized crime, called "Criminals Without Borders" went on as 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 activists to "Smash (the) WEF."
The flyer says: "Let us fight together against the unbearable propaganda of capitalism."
Hobi said he expects Saturday's demonstration to be peaceful.
In previous years radical activists have stayed away from the chic ski resort and staged violent demonstrations elsewhere in Switzerland instead.