CLAY COUNTY, Fla. -

A heart surgeon and a transplant technician from Mayo Clinic and a helicopter pilot died early Monday morning when the aircraft they were flying to harvest organs at Shands Medical Center in Gainesville crashed in woods in southern Clay County.

The St. Augustine-based helicopter chartered by Mayo went down just before 6 a.m., but the wreckage wasn't found for several hours.

A Clay County deputy in a helicopter spotted wreckage in woods off Hogarth and Dynamite roads, southwest of Green Cove Springs.  Deputies, who used ATVs to reach the site and confirm that there were no survivors, said you could see where the rotors chopped down trees as it descended.

"The wreckage was probably a mile back in the woods," said Clay County Lt. Russ Burk. "It's another four miles to before you get to another road, so it's way back in the woods in the middle of nothing."

Officers who had been to the scene said the helicopter broke into pieces upon impact. A small woods fire started by the crash was quickly contained, but the site remained shrouded in smoke in the late afternoon.

Mayo Clinic identified the two employees killed as Dr. Luis Bonilla and technician David Hines. The team was to retrieve a heart and other organs in Gainesville for transplants in Jacksonville.

The heart could not be used in another transplant because its viability expired, and the patient who had been scheduled to receive it continues to wait for a new organ, Mayo Clinic spokesman Layne Smith said Monday evening.

"As we mourn this tragic event, we will remember the selfless and intense dedication they brought to making a difference in the lives of our patients," said John Noseworthy, Mayo Clinic president and chief executive officer. "We recognize the commitment transplant teams make every day in helping patients at Mayo Clinic and beyond. Our thoughts and prayers are with the families."

Channel 4 learned the heart that was to be brought to Jacksonville for a waiting patient is no longer viable.

WJXT is told that the Bell 206 helicopter was owned by SK Logistics. The name of the pilot who died has not been identified.

The Jacksonville Sheriff's Office sent one of its helicopters to assist with the search, which at one point included parts of Flagler, Putnam and Clay counties.

A National Transportation Safety Board team from Miami was expected to arrive at the crash site Monday evening to take charge of the investigation.