An explosion in Prague's historic district has left dozens injured. Rescue workers were searching the rubble for missing persons. Meanwhile, the confusion has brought life in the Czech Republic's capital to a standstill.Emergency services led sniffer dogs through the explosion site on Monday to account for any missing people following a blast that tore through a building near Prague's Charles University.Initial reports had said authorities feared up to four people had been killed in the area frequented by tourists. About 15 people were reportedly in the building, which included an office of the International Air Transport Association and an art gallery.Some 35 people in the surrounding area sustained injuries, according to Zdenek Schwarz, the head of Prague's rescue service. Authorities had originally said 40 had been injured in the blast.Witnesses on site described a powerful blast that caused damage to nearby streets, including shattering windows at historical sites such as the National Theater."There was glass everywhere and people shouting and crying," Vaclav Rokyta, a student, told the Associated Press."The blast was strong. ... The shockwave knocked people off their feet, but there were no serious injuries in the AV," Science Faculty employee Michaela Mazancova, told the news agency dpa.Prague's mayor, Bohuslav Svoboda, confirmed that a gas leak was believed to have caused the explosion, calming fears of a terrorist attack.Prime Minister Petr Necas said he was deeply affected by "the tragedy of the gas explosion."The blast occurred on Monday morning around 10 a.m. on Divadelni Street near the university's Faculty of Science and the Film and TV School of the Academy of Sciences of Performing Arts.