The Transportation Safety Board believes a whiteout caused a plane crash in western Manitoba last winter that killed a pilot and three children.
The board says in its report that fog rolled in shortly after the Cessna took off near the small town of Waskada on Feb. 10, 2013.
It says the weather, combined with snow-covered ground, likely made it difficult for the pilot to see the horizon.
The board says the pilot probably got disoriented and the plane flew into a farmer's field.
Darren Spence was an experience crop duster who had taken his two sons and their friend on a pleasure flight that day.
Gage Spence, was 10, his brother Logan, was nine, and Dawson Pentecost was also nine.
At the time, family said Dawson's father, a volunteer firefighter, was one of the first to get to the wreckage and discovered that no one had survived.