A fire swept through one of Costa Rica's main hospitals early on Tuesday, killing 17 people, mostly critically ill patients trapped in the five-story building's upper floors. The blaze broke out shortly before 2:30 a.m. at the Rafael Angel Calderon Guardia Hospital in San Jose, trapping patients in the neurosurgery and intensive care wards on the top two floors, a Red Cross official said, according to Reuters. Local television reported that the fire started in a central stairwell in the public hospital. Hospital and emergency services were not immediately available for comment. Sixteen patients and one nurse were killed in the blaze, which triggered several small explosions. Witnesses said critically ill patients tried to escape from balconies and windows on the top floor. "It was a terrible scene," Jose Bismar Morales, who works at a nearby lab, told Reuters outside the charred hospital. "People on the fifth floor were trying to throw themselves off the balcony. Old people were running and it was very difficult to help them." --More 2303 Local Time 2003 GMT