Six people, including one infant, were missing while two others had been rescued late on Sunday after a float plane crashed off Western Canada's rocky coast.

One female passenger and the pilot of the DeHavilland Beaver aircraft were flown to an area hospital and are in stable condition, Navy Lieutenant Paul Pendergast told AFP.

The commercial passenger plane was en route to Vancouver when it crashed into Lyall Harbour after taking off near Saturna Island, 50 kilometers south of Vancouver near the Canada-United States border.

Pendergast said several boats, a military Search and Rescue helicopter and airplane and Coast Guard divers were searching for the plane, which was thought to be in about 14 meters of water.

"We have a pretty good idea where the aircraft is, but it's very dark... even for divers with lights," said Pendergast.

There was no immediate explanation for the crash, which occurred just eight minutes before local sunset, said Pendergast.

"There's no indication of foul or inclement weather... They were stopping there to pick up passengers on the way to Vancouver."