SAN FRANCISCO, May 27 (Xinhua) -- One man was reported missing after a small plane crashed in Eagle Harbor in King County in the west U.S. state of Washington Sunday, U.S. Coast Guard Pacific Northwest said.

Two people were on board the plane, a 1974 4-cycle two-seater fixed wing single engine when it crashed, and a 60-year-old woman was rescued and transported to Harborview Medical Center in Seattle, the state's largest city, the Coast Guard tweeted Sunday evening.

The female passenger is in critical condition, a local TV report said.

The small aircraft was reported to have crashed and sunk in Eagle Harbor under "unknown circumstances," the K5 News TV channel quoted an official with the U.S. Federal Aviation Administration as saying.

The Coast Guard dispatched a rescue helicopter and a boat crew for search operations, in collaboration with the staff of the Seattle Fire Department, said K5 News.

The cause of the crash is under investigation.