As many as 160 people may have died in Albania Saturday when a powerful explosion ripped an army depot outside Tirana, officials said. While exact casualty figures were unknown, a spokeswoman for Albanian Prime Minister Sali Berisha said officials were concerned U.S. citizens working at the military site may have been among the victims of the large blast, The Guardian reported. "We do not know the exact number, but we fear the worst for the three teams, each of 21 people, working there at the time," spokeswoman Juela Mecani said. "Several were U.S. citizens." Officials at the U.S. embassy in the Albanian capital had no news regarding the condition of U.S. citizens reportedly at the blast site, the BBC said.Meanwhile, Sky News said the explosion was so powerful windows on homes six miles away were blown out by the ensuing shock wave. The capital's international airport also suffered damage from the powerful concussion, the British broadcaster added.