A medical helicopter returning to its base with a pilot and two nurses aboard crashed into Puget Sound (search), apparently killing all three people, authorities said.

Human remains and aircraft wreckage were found early Friday, hours after the Airlift Northwest helicopter lost contact with dispatchers late Thursday, authorities said.

Officials at a National Transportation Safety Board briefing said side-scan radar on a Coast Guard vessel is looking for the wreckage. The helicopter apparently sank in 300 feet of water, Edmonds police Sgt. Jeff Jones said.

They've been identified as 59-year-old pilot Steve Smith and the nurses, 49-year-old Perin Reed and 47-year-old Lois Suzuki. All worked for Airlift Northwest (search).

The debris was found in an area of Puget Sound called Browns Bay, just north of Edmonds, said Coast Guard Petty Officer Adam Eggers. Jones said papers found floating about a mile offshore identified the aircraft.

The helicopter had been returning to Arlington airport from Harborview Medical Center in Seattle, about a 40-mile trip. There were areas of fog and mist and some gusty winds at the time.

A resident called 911 shortly after 9 p.m. and reported hearing a helicopter fly over, then an explosion, Jones said.

Airlift Northwest, based in Seattle, provides emergency air transport service for critically ill or injured patients in Washington, Alaska, Montana, Idaho and western Canada, its Web site said.