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DAVOS, Switzerland, Jan 27 (Reuters) - Left-wing activists claimed responsibility for a minor explosion on Thursday at a hotel in Davos, close to where top executives and world leaders were meeting, but nobody was hurt.

Devin Wenig, CEO of Thomson Reuters’ Markets division, was in a breakfast meeting of senior executives at the hotel when the explosion happened.

“A huge boom went off. The whole ceiling lifted. Everyone was convinced it was a bomb,” he said. “It took a half hour to reassemble the meeting.”

Participants were later told that a boiler had exploded, he added. The Forum’s main programme was not disrupted.

“I can confirm that there has been an explosion in a storage room in the basement of the hotel,” Thomas Hobi, a spokesman for the local police said. “There has been minor damage but nobody was injured.”

Swiss prosecutors said they were investigating the explosion, implying that there might be a criminal motive, but they declined to give further details.

A Reuters photographer said a few police were patrolling outside the building and he could see a broken window but no other damage.

A group calling itself Revolutionary Perspective said in a statement on an activist website it had targeted the luxury Posthotel with a firebomb and said Swiss ministers and representatives of top bank UBS were staying there.

“Our fight against the dictatorship of capital is focused on the social alternative to capitalism: communism,” the group said in the statement.

A spokesman for the World Economic Forum (WEF) said police had made two bomb sweeps of the hotel after a threat posted online. The WEF said in a statement that the blast had been caused by a small firework at the back entrance of the hotel.

“The police is investigating this incident. The hotel is fully operational and accessible,” it said.

The luxury Posthotel is in the heart of Davos village, a few hundred metres (yards) from the WEF congress centre where hundreds of company heads, central bankers and politicians are meeting.

On Wednesday, Swiss police evacuated a building and removed a suspicious object in the town St. Gallen, 80 km north of Davos, after a threat from the same group, saying they wanted to target the opening of the WEF meeting. (Reporting by Silke Koltrowitz and Emma Thomasson; editing by Philippa Fletcher)