CORONADO, Calif. - Officials say a Navy helicopter has made a "hard landing" at North Island Naval Air Station in Southern California, injuring four crew members on board.

Navy officials said in a release that the MH-60R Seahawk helicopter was taking part in routine training at the station in San Diego County when it made the hard landing at about 11 p.m. Wednesday.

Officials say two of the crew members were taken to UC San Diego Medical Center and the other two were taken to Scripps Mercy Hospital. The extent of their injuries wasn't released.

The news release says an "aircraft mishap investigation" is under way.