All passengers have been accounted for after a seaplane made an emergency landing near Sucia Island before catching fire.

Kenmore Air, the largest U.S. seaplane airline, said a de Havilland DHC-3 Otter plane that departed from Lake Union, Seattle, was involved in an accident in Shallow Bay near Sucia Island at about 5.15pm PDT on Thursday.

The airline said there were 10 passengers and one pilot on board.

An image released by the Coast Guard showed the seaplane on fire in the water at the crash site.

Sucia Island is in Washington state's San Juan Islands, located north of Seattle near the Canadian border.

The U.S. Coast Guard said all 11 people on board were accounted for following a rescue operation involving Canadian and local responders.

"Several patients are being transported to local hospitals for medical evaluation and treatment," it added.

Two injured passengers were transported to medical facilities in Bellingham and another two injured passengers were transported to Orcas Island for evaluation and treatment.

"Kenmore Air is fully cooperating with the investigating authorities, and we will continue providing verified information as it becomes available," CEO David Gudgel said.

Founded in 1946, Kenmore Air flies more than 90,000 passengers annually on scheduled, scenic and charter flights, according to its website.