The red and white private Beech 35 aircraft went missing after departure Saturday at 4:00 pm (2200 GMT), and family members informed authorities when the plane never arrived, according to the Washington State Department of Transportation.
"The last cell phone signal from one of the plane's occupants was detected at about 11:30 pm," the agency said in a statement.
A search yesterday turned up no signs of the aircraft, and rescue workers will continue the hunt after daybreak today.
It added that crews would "continue working through the night on planning and logistics."
The agency identified the three passengers as Leland Bowman, 62, his wife Sharon Bowman, 63 and their step-granddaughter Autumn Veatch, 16.