BELLINGHAM, Wash. — Officials say a pilot is dead after a small plane headed to Bellingham for maintenance crashed in the Chuckanut Mountains in northwestern Washington.

Federal officials say the single-engine Mooney M20K departed from Paine Field in Everett and crashed near the Bellingham International Airport Monday night.

The cause of the crash is unknown.

A U.S. Customs and Border Patrol helicopter found the wreckage using a signal from the plane’s last known location and direction of travel.

Whatcom County Undersheriff Jeff Parks says only the pilot was on board the plane when it crashed.

Whatcom County medical examiner Dr. Gary Goldfogel says the pilot was 61-year-old Don Stanwyck.

Goldfogel says his cause of death is under continuing investigation and that Stanwyck had pre-existing heart disease that may have created a medical emergency and partial explanation for the crash.

The National Transportation Board will investigate.