Two Connecticut residents and another passenger were killed Wednesday in a small plane crash in Maryland.

The Piper Pa-30, which was registered to Greg Doppke of Greenwich, Connecticut, took off from the Westchester County Airport and was heading for North Carolina. Authorities are not sure what caused the plane to go down in Maryland. They say contact with the pilot was lost shortly after 9:30 a.m.

Also killed in the crash was Doppke's business partner, Richard Lomas, of Stamford, Connecticut. Doppke is the head of an air conditioning business in Hawthorne, Westchester. Both victims were identified by a contractor's trade group. The third victim has not yet been identified.

Federal investigators are in Maryland to sift through wreckage in an effort to find out what happened.