VANCOUVER - Intoxicated passengers likely interfered with a pilot just moments before his float plane crashed and killed all four people onboard off the west coast of Vancouver Island last year, says a recently released report.

Atleo River Air Service pilot Damon York and passengers Katrina English, Edward Sam and Samantha Mattersdorfer died when their Cessna 185F plane crashed just northwest of Tofino, B.C., on May 29, 2010.

The report by the Transportation Safety Board of Canada ruled out mechanical and environmental issues in the crash and said the pilot was not incapacitated because of a medical issue.

Investigators found that the plane struck the ocean at a speed and angle consistent with a deliberate nose dive or loss of control, and the report said based on the pilot's demeanour, there was no reason for him to dive to the point of impact.

"What was happening in the cabin moments before the pilot lost control cannot be accurately determined," it said. "However, it can be concluded that this probably involved activity by the unsecured passengers that interfered with the pilot and his control of the aircraft."

Toxicology tests showed all three passengers were highly intoxicated.

The report said it's possible a passenger seated behind the pilot kicked the pilot's seat forward and held it, forcing the controls forward and the pilot into the instrument panel.

Because the pilot was not wearing his shoulder strap and because the pilot's seat didn't have a locking mechanism, he wouldn't have been able to stop the interference, the report said.

It also said the passengers were so drunk that they likely didn't realize the seriousness of the situation in time to allow the pilot to regain control of the plane.

"The passengers were intoxicated at the time they boarded the aircraft, and had previously been argumentative. The final location of some beer cans and fragments of the beer case indicate that the case of beer was in proximity to the passengers before impact."

The pilot suffered severe injuries to his forehead and a broken right wrist, and the passenger seated directly behind him suffered two broken ankles, said the report.

Except for the front passenger who died on impact, everyone on board died as a result of drowning and blunt-force trauma.

Officials at the Ahousaht First Nation band office declined comment Thursday. Nobody from Atleo River Air Service was immediately available for comment.