Crews combing Lake Erie for a plane carrying six people that disappeared overnight shortly after takeoff from a Cleveland airport along the shore are still hopeful that the occupants could be found alive, a Coast Guard official said Friday, AP reported. Authorities have "faint hints" but no strong pulse from an emergency locating transmitter, a beacon that could help find the plane carrying three children and three adults, said Capt. Michael Mullen, the chief of response for the Ninth Coast Guard District. The crews searching for the plane are in search-and-rescue mode, not recovery mode, as they ply waters that are about 50 feet deep, he said. "We're very hopeful. We will be very hopeful up until the point that we have to turn the search off and we switch over to assisting with recovery," Mullen said. The Columbus-bound Cessna Citation 525 departed Burke Lakefront Airport late Thursday with six aboard and vanished from radar about 2 miles over the lake. Why remains unclear. Searchers have found no sign of debris. Snow squalls, higher seas and darkness made nighttime searching difficult, Mullen said. Weather prevented a boat search overnight, but a U.S. Coast Guard helicopter and a Canadian air crew in a plane were being used, and ship from Detroit was being brought in to help with the search.