There were 10 people, including one child, aboard the plane, according to the Coast Guard.
The Coast Guard said it received a report about the crashed plane around 3:11 p.m. local time. The plane took off from Friday Harbor, Washington, and was en route to Seattle Tacoma International Airport, the Coast Guard said. The Coast Guard had initially stated there were nine people aboard the plane.
The Coast Guard said it was using boats, helicopters, Ospreys and other aircraft in the search. Emergency responders from South Whidbey Fire, Island County Sheriff's Office and Snohomish County Sheriff's Office were also assisting in the search, the Coast Guard said.
"The Coast Guard is still in the Search and Rescue phase of operations, and we will actively continue to search for the missing individuals throughout the evening," the Coast Guard told CBS News.
Information on the specific type of plane and what may have caused the crash was not immediately available.
ZZ/PR