PRAGUE — A powerful blast believed to be a gas explosion ripped open an office building in the center of Prague on Monday, injuring at least 35 people and sending shock waves through the Old Town tourist district.
The blast shattered windows in the scenic area of charming streets and postcard-pretty buildings, sending glass flying. Authorities closed a wide area around the site and some tourists were stranded on street corners with baggage-loaded trolleys, unable to get into their hotels.
Authorities said two or three people were still believed to be missing, but sniffer dogs searching the rubble had not indicated that anyone was buried and the prime minister said it appeared no one had died.
An AP cameraman filming at the time of the blast said the physical impact could be felt on the famed 15th-century Charles Bridge over the Vltava River, which was packed with tourists.
The explosion occurred on Divadelni Street at about 10 a.m., in one of a row of several-story-tall brick buildings dating back about a century. The street was covered with rubble and police evacuated people from nearby buildings.
‘‘It’s really immense and huge, almost like after an air assault or a bomb explosion,’’ Prime Minister Petr Necas said after visiting the scene. ‘‘So, if we really prove what we think right now, which is that nobody died, it was very lucky.’’
Prague mayor Bohuslav Svoboda ruled out a terrorist attack, saying the blast was a gas explosion.
Prague is a major tourist capital, visited every year by legions of students, backpackers, and others from around the world. In 2012, a total of 5.4 million people visited, with a large majority from outside the country — many from Germany, Russia and the United States.
Officials had estimated that up to 40 were injured, but Zdenek Schwarz, head of rescue service in Prague, later narrowed that down to 35.