(CNN) Two people died when a single-engine plane crashed Saturday morning at a general aviation airport on the north shore of Oahu in Hawaii, authorities said.

Federal Aviation Administration spokesman Ian Gregor told CNN in an email that a Cessna 305A took off about 9:15 a.m. local time from Dillingham Airfield, crashed for unknown reasons and came to rest upside down.

The FAA and the National Transportation Safety Board are investigating, Gregor said. Hawaii Department of Transportation spokesman Tim Sakahara told CNN affiliate KITV that the lead NTSB investigator is expected to arrive Sunday.

Bill Star, the vice president and general manager of Honolulu Soaring, a flight school, told CNN that two men were "getting familiar with the airplane" during a flight at the airfield when the plane crashed.

Star said the men were an instructor and a pilot who had "lots of experience" with different types of aircraft.