A boat carrying tourists on a senior citizens' cruise overturned Sunday on a calm, chilly lake in upstate New York, killing at least 21 people and sending more than two dozen cold and wet passengers to a hospital. The accident may have occurred when the boat was hit by the wake of a larger passing vessel, Warren County Sheriff Larry Cleveland said. "We haven't ruled anything out yet," he said. The boat was carrying a tour group from the Trenton, Michigan, area and was sailing just north of the village of Lake George, a popular tourist destination. With calm waters, clear skies and temperatures in the 70s (about 21 Celsius), it seemed perfect boating weather. The 40-foot (12-meter) Ethan Allen capsized around 3 p.m. on Lake George about 50 miles (80 kilometers) north of Albany in the Adirondack Mountains. The accident apparently happened so fast that none of the passengers were able to put on a life jacket, Cleveland said. Adult boat passengers are not required to wear a life jacket in New York. Patrol boats that reached the scene within minutes found other boaters already pulling people from the water. All passengers had been accounted for within two hours. Twenty-seven people were taken to a hospital in nearby Glens Falls. Some suffered broken ribs and some complained of shortness of breath. The boat had a maximum capacity of 50 people; it was carrying as many as 49. The sheriff said there was still confusion over the number of passengers, and investigators were interviewing survivors to get a solid count. The National Transportation Safety Board was expected at the lake Monday. Representatives of Shoreline Cruises, which operates the boat, could not immediately be reached for comment. The boat's owner, Jim Quirk, whose family has operated Shoreline Cruises for decades, told the Glens Falls Post-Star: "It is a tragedy and it's very unfortunate." "Nothing of this magnitude has ever happened," state police Superintendent Wayne Bennett said. "It's unprecedented."