Four people are dead after a float plane crash on a small island off the northern tip of Vancouver Island.

The Cessna 208 Caravan float plane went down on Addenbroke Island, approximately 82 kilometres north of Vancouver Island, with nine people on board Friday morning.

The Transportation Safety Board confirmed Friday evening that the plane belongs to Seair Seaplanes of Vancouver.

Two Royal Canadian Air Force aircraft – a CH-149 Cormorant rescue helicopter and a CC-115 Buffalo patrol plane – were dispatched shortly after noon from the 442 Transport and Rescue Squadron based out of Comox, according to Maritime Forces Pacific.

A coast guard helicopter was also on scene and three coast guard vessels attended the waters off Addenbroke shortly after the crash.

Survivors were hoisted into the Cormorant helicopter at approximately 5 p.m. and were airlifted to emergency health services in Port Hardy.

Multiple ground and air ambulance crews were also mobilized, including two air ambulance jets, according to BC Emergency Health Services. The agency said two patients are in critical condition and the other three are in serious, but stable condition.

The plane was headed for Calvert Island, approximately three and a half kilometres from Addenbroke, when it crashed shortly after 11 a.m. The TSB says the chartered flight took off from a water aerodrome near Vancouver International Airport.

Seair issued a statement Friday evening, confirming the downed aircraft belonged to the company.

"We are currently working with first responders and authorities and have immediately suspended all flights," a spokesperson for the airline said. 

"Our thoughts are with those involved in the crash and their loved ones and [we] are devastated by this fatal accident."

The Joint Rescue Coordination Centre confirmed at 3 p.m. that four people died in the crash. The JRCC could not confirm the extent of the injuries of the other five people on board.

The BC Ferries vessel Northern Sea Wolf was in the area standing by for assistance in the immediate aftermath of the crash, a spokesperson for the ferry service said.

B.C. Premier John Horgan offered his condolences via Twitter on Friday evening, writing, "My thoughts are with those affected by this tragic accident. Thank you to the coast guard, BC Ferries, medical staff & others on-scene We'll continue to closely monitor the situation." 

The Cessna 208 Caravan is a single-engine turboprop plane which can be configured to seat either 9 or 14 passengers, plus one pilot.

A weather observation station on the Addenbroke Island lighthouse facility indicates there was heavy cloud cover, moderate winds and light rain at the time of the crash.