Investigators suspect that a plane that crashed outside Port Hope Simpson descended rapidly and vertically in the flight's final minutes. (CBC)

A plane that crashed on Sunday while heading to pick up an ill patient in southern Labrador descended rapidly, and vertically, in its final minutes, an investigator says.

Three investigators with the Transportation Safety Board of Canada were in Port Hope Simpson on Wednesday to analyze the wreckage of a small plane that was commissioned to fly a patient in the community to a hospital in northern Newfoundland.

Pilot James Hudson, 43, was killed in the crash, which occurred in a wooded area about five kilometres outside of the community. He was alone on the flight.

Michael Cunningham, the Atlantic regional manager with the TSB, said it appeared that the plane almost fell from the sky.

"There are trees on either side of the impact outline which have not been touched by the aircraft, so that would indicate that there was not much of a horizontal component to the direction of flight. It was pretty much vertical," he said.

"It's not normal, obviously, for an aircraft to be descending vertically like that."

There was fog in the area at the time of the crash, but Cunningham said it is too soon to say if that was a factor. RCMP said earlier this week that Hudson had talked about the fog he saw with ground crew in the flight's final minutes.

Cunningham said the small plane did not have a black box recorder, but its global positioning system was recovered.

Cunningham said it looks like the plane's engine was running and that the plane itself was intact before the impact.

However, he said the intense fire did not leave many clues behind.

"Our task is quite daunting because of the fact that there was such extensive damage to the aircraft in the post-crash fire," he said.

Still, he said he expects the TSB will be able to determine what caused the crash.