A medical transport plane carrying six people went down Monday afternoon in Lake Michigan, authorities said. There was no word on survivors. Two crew members and four passengers were aboard the jet, which had just left General Mitchell International Airport, Milwaukee Fire Lt. Lawrence Jenkins said. Medical transport planes typically carry patients or organs for transplants, he said, but he did not know what the plane was transporting or where it was headed. The Milwaukee Police Department notified the Coast Guard that a plane went missing about 4 p.m., Petty Officer David Warfel said. The Coast Guard found the plane about 20 minutes later, he said. Pat Rowe, spokeswoman for the airport, said a Cessna Citation dropped off the radar about 4 p.m. (2100 GMT). She did not know if the Cessna had issued any distress signals.